Myosin VI stabilizes intercellular junctions in the testis through the LHR and MAPK signalling pathway during spermatogenesis in Eriocheir sinensis

The myosin motor protein myosin VI plays an essential role in mammalian spermatogenesis, however, the effects of myosin VI on male reproduction in Crustacea remain obscure. We identified the macromolecule es-Myosin VI in Eriocheir sinensis, and studied it by multiple methods. It co-localized with F-actin and was highly expressed in the testis. We interfered es-Myosin VI using dsRNA in vivo, an apparent decrease in spermatozoa count was detected. We also found that the MAPK signalling pathway was changed, subsequently causing disruption of intercellular junctions and damage to the functional hemolymph-testis barrier. We observed that luteinizing hormone receptor es-LHR was located within seminiferous tubules, which was different from the expression in mammals. Es-LHR could bind with es-Myosin VI in testis of E. sinensis, its localization was significantly altered when es-Myosin VI was deleted. Moreover, we obtained consistent results for the MAPK signalling pathway and spermatogenesis defects between the es-LHR and es-Myosin VI knockdown groups. In summary, our research demonstrated that knockdown of es-Myosin VI disturbed the intercellular junction and HTB function via the MAPK signalling pathway by changing the localization of es-LHR in the testis of E. sinensis, which was the potential reason for its negative impact on spermatogenesis.

mTORC1/rpS6 and mTORC2/PKC regulate spermatogenesis through Arp3-mediated actin microfilament organization in Eriocheir sinensis

Mammalian target of rapamycin (mTOR) is a crucial signaling protein regulating a range of cellular events. Numerous studies have reported that the mTOR pathway is related to spermatogenesis in mammals. However, its functions and underlying mechanisms in crustaceans remain largely unknown. mTOR exists as two multimeric functional complexes termed mTOR complex 1 (mTORC1) and mTORC2. Herein, we first cloned ribosomal protein S6 (rpS6, a downstream molecule of mTORC1) and protein kinase C (PKC, a downstream effector of mTORC2) from the testis of Eriocheir sinensis. The dynamic localization of rpS6 and PKC suggested that both proteins may be essential for spermatogenesis. rpS6/PKC knockdown and Torin1 treatment led to defects in spermatogenesis, including germ cell loss, retention of mature sperm and empty lumen formation. In addition, the integrity of the testis barrier (similar to the blood-testis barrier in mammals) was disrupted in the rpS6/PKC knockdown and Torin1 treatment groups, accompanied by changing in expression and distribution of junction proteins. Further study demonstrated that these findings may result from the disorganization of filamentous actin (F-actin) networks, which were mediated by the expression of actin-related protein 3 (Arp3) rather than epidermal growth factor receptor pathway substrate 8 (Eps8). In summary, our study illustrated that mTORC1/rpS6 and mTORC2/PKC regulated spermatogenesis via Arp3-mediated actin microfilament organization in E. sinensis.

TiO2 nanoparticles affect spermatogenesis and adhesion junctions via the ROS-mediated mTOR signalling pathway in Eriocheir sinensis testes

Recent findings found that TiO₂ nanoparticles (TiO₂-NPs) have male reproductive toxicity. However, few reports have studied the toxicity of TiO₂-NPs in crustaceans. In this study, we first chose the freshwater crustacean Eriocheir sinensis (E. sinensis) to explore the male toxicity of TiO₂-NP exposure and the underlying mechanisms. Three nm and 25 nm TiO₂-NPs at a dose of 30 mg/kg bw induced apoptosis and damaged the integrity of the haemolymph-testis-barrier (HTB, a structure similar to the blood-testis-barrier) and the structure of the seminiferous tubule. The 3-nm TiO₂-NPs caused more severe spermatogenesis dysfunction than the 25-nm TiO₂-NPs. We initially confirmed that TiO₂-NP exposure affected the expression patterns of adherens junctions (α-catenin and β-catenin) and induced tubulin disorganization in the testis of E. sinensis. TiO₂-NP exposure caused reactive oxygen species (ROS) generation and an imbalance of mTORC1-mTORC2 (mTORC1/rps6/Akt levels were increased, while mTORC2 activity was not changed). After using the ROS scavenger NAC to inhibit ROS generation, both the mTORC1-mTORC2 imbalance and alterations in AJs were rescued. More importantly, the mTORC1 inhibitor rapamycin abolished mTORC1/rps6/Akt hyperactivation and partially restored the alterations in AJs and tubulin. Collectively, the mTORC1-mTORC2 imbalance induced by TiO₂-NPs was involved in the mechanism of AJ and HTB disruption, resulting in spermatogenesis in E. sinensis.

Es-β-CATENIN affects the hemolymph-testes barrier in Eriocheir sinensis by disrupting cell junctions and cytoskeleton

β-CATENIN is an evolutionarily conserved multifunctional molecule that maintains cell adhesion as a cell junction protein to safeguard the integrity of the mammalian blood-testes barrier, and also regulates cell proliferation and apoptosis as a key signaling molecule in the WNT/β-CATENIN signaling pathway. In the crustacean Eriocheir sinensis, Es-β-CATENIN has been shown to be involved in spermatogenesis, but the testes of E. sinensis have large and well-defined structural differences from those of mammals, and the impact of Es-β-CATENIN in them is still unknown. In the present study, we found that Es-β-CATENIN, Es-α-CATENIN and Es-ZO-1 interact differently in the testes of the crab compared to mammals. In addition, defective Es-β-CATENIN resulted in increased Es-α-CATENIN protein expression levels, distorted and deformed F-ACTIN, and disturbed localization of Es-α-CATENIN and Es-ZO-1, leading to loss of hemolymph-testes barrier integrity and impaired sperm release. In addition to this, we also performed the first molecular cloning and bioinformatics analysis of Es-AXIN in the WNT/β-CATENIN pathway to exclude the effect of the WNT/β-CATENIN pathway on the cytoskeleton. In conclusion, Es-β-CATENIN participates in maintaining the hemolymph-testes barrier in the spermatogenesis of E. sinensis.

es-Arp3 and es-Eps8 regulate spermatogenesis via microfilaments in the seminiferous tubule of Eriocheir sinensis

Spermatogenesis is a complicated process that includes spermatogonia differentiation, spermatocytes meiosis, spermatids spermiogenesis and final release of spermatozoa. Actin-related protein 3 (Arp3) and epidermal growth factor receptor pathway substrate 8 (Eps8) are two actin binding proteins that regulate cell adhesion in seminiferous tubules during mammalian spermatogenesis. However, the functions of these two proteins during spermatogenesis in nonmammalian species, especially Crustacea, are still unknown. Here, we cloned es-Arp3 and es-Eps8 from the testis of Chinese mitten crab Eriocheir sinensis. es-Arp3 and es-Eps8 were located in spermatocytes, spermatids and spermatozoa. Knockdown of es-Arp3 and es-Eps8 in vivo caused morphological changes to seminiferous tubules including delayed spermatozoa release, shedding of germ cells and vacuoles. Filamentous-actin (F-actin) filaments network was disorganized due to deficiency of es-Arp3 and es-Eps8. Accompanying this, four junctional proteins (α-catenin, β-catenin, pinin and ZO1) displayed abnormal expression levels as well as penetrating biotin signals in seminiferous tubules. We also used the Arp2/3 complex inhibitor CK666 to block es-Arp3 activity and supported es-Arp3 knockdown results. In summary, our study demonstrated for the first time that es-Arp3 and es-Eps8 are important for spermatogenesis via regulating microfilament-mediated cell adhesion in Eriocheir sinensis.

[Application of the two-step sentinel lymph node biopsy with double-tracer in early staged endometrial cancer]

Objective: To explore the feasibility and clinical value of sentinel lymph node (SLN) biopsy through cervix-uterine combined two-step injection with two tracers in patients with early stage endometrial cancer. Methods: From July 2019 to April 2021, a total of 73 patients, aged (54.2±3.3) year, who were preoperatively diagnosed as stage Ⅰ-Ⅱ endometrial cancer (including 56 low-risk patients and 17 medium-high risk patients) in Affiliated Hospital of Qingdao University were selected. According to the different sites of tracer injection, the patients were randomly divided into three groups: cervical injection group (25 cases): 1 ml of nano-carbon was used to inject at 3 and 9 o'clock in the cervix; uterine injection group (21 cases): the magnetic resonance imaging examination was performed to determine the location of the lesion, and 4 ml of methylene blue was injected into the uterine body at 2 sites where the lesion was located; combined injection group (27 cases): cervical injection of nano-carbon (1 ml) combined with uterine injection of methylene blue (4 ml). The SLN in all patients were identified under laparoscopy, removed, and followed by frozen pathological examination. Pathological ultra-staging was performed if the postoperative pathological outcome of SLN was negative. The total detection rate of SLN, bilateral pelvic SLN detection rate, sensitivity, negative predictive value, and location of SLN in each group were calculated and compared. Results: (1) In 73 patients with endometrial cancer, the overall detection rate of SLN was 88% (64/73), the detection rate of bilateral pelvic SLN was 67% (49/73), and the detection rate of para-aortic SLN was 49% (36/73). The overall detection rate of SLN (71%, 15/21) and bilateral pelvic SLN (43%, 9/21) in the intrauterine injection group were significantly lower than those in the cervical injection group [92% (23/25), 76% (19/25), respectively] and the combined injection group [96% (26/27), 78% (21/27), respectively; all P<0.05]; the detection rate of para-aortic SLN in the cervical injection group (28%, 7/25) was significantly lower than those in the intrauterine injection group and combined injection group [52% (11/21) and 67% (18/27), respectively; both P<0.05]. Among 73 cases with endometrial cancer, 9 had lymph node metastasis confirmed by postoperative pathological examination, 8 of them had lymph node metastasis detected by SLN and 1 had no lymph node metastasis detected by SLN, with a total sensitivity of 89% and a negative predictive value of 98%. The sensitivity and negative predictive value of cervical injection group and combined injection group were 100%, while the sensitivity and negative predictive value of intrauterine injection group were 67% and 95%. Among 56 low-risk patients, only one patient with lymph node metastasis was confirmed by postoperative pathology by SLN detection, and the metastasis rate was 2% (1/56), and the sensitivity and negative predictive value were 100%. Lymph node metastasis was confirmed in 8 of 17 patients (8/17) with a sensitivity of 88% and a negative predictive value of 90%. (2) A total of 459 SLN were detected in 73 endometrial cancer patients, with the highest proportion of external iliac (33.3%, 153/459).The obturator foramen was 25.3% (116/459), para-aortic 19.6% (90/459), iliac 12.0% (55/459), and presacral 9.8% (45/459). The proportion of para-aortic SLN in the cervical injection group was 12.4% (21/169), which were significantly lower than that in the intrauterine injection group and the combined injection group [27.4% (26/95) and 22.1% (43/195), respectively; both P<0.05]. (3) Pathological super-staging results: among 64 patients with negative SLN routine paraffin pathology, 4 cases of lymph node micro-metastases and 1 case of isolated tumor cell metastasis were detected, and the SLN micro-metastases rate was 8% (5/64), including 2 cases of low-risk patients and 3 cases of medium-high risk patients. Conclusions: SLN biopsy has high sensitivity and negative predictive value in patients with early endometrial cancer and could be used as an alternative to systematic lymph node dissection in low-risk patients. The SLN mapping through cervical-uterine combined injection could further improve the detection rate effectively and avoid the missed detection of positive para-aortic lymph node, especially for high-risk patients or patients with fundal tumor involvement.

Quantum circuits with many photons on a programmable nanophotonic chip

Growing interest in quantum computing for practical applications has led to a surge in the availability of programmable machines for executing quantum algorithms1,2. Present-day photonic quantum computers3-7 have been limited either to non-deterministic operation, low photon numbers and rates, or fixed random gate sequences. Here we introduce a full-stack hardware-software system for executing many-photon quantum circuit operations using integrated nanophotonics: a programmable chip, operating at room temperature and interfaced with a fully automated control system. The system enables remote users to execute quantum algorithms that require up to eight modes of strongly squeezed vacuum initialized as two-mode squeezed states in single temporal modes, a fully general and programmable four-mode interferometer, and photon number-resolving readout on all outputs. Detection of multi-photon events with photon numbers and rates exceeding any previous programmable quantum optical demonstration is made possible by strong squeezing and high sampling rates. We verify the non-classicality of the device output, and use the platform to carry out proof-of-principle demonstrations of three quantum algorithms: Gaussian boson sampling, molecular vibronic spectra and graph similarity8. These demonstrations validate the platform as a launchpad for scaling photonic technologies for quantum information processing.

[Clinical analysis of surgical treatment of post-infarction left ventricular aneurysm: a series of 254 patients]

Objective: To examine the efficacy of two surgical procedures on post-infarction left ventricular aneurysm. Methods: The clinic data of 254 patients with post-infarction left ventricular aneurysm, who underwent surgical ventricular reconstruction between January 1997 and December 2019 in Department of Cardiovascular Surgery, Nanjing Hospital Affiliated to Nanjing Medical University was analyzed retrospectively. There were 183 males and 71 females aged from 31 to 81 years, with a median age of 64.6 years. Based on the size of the ventricular aneurysm, there were 73 patient received linear reconstruction (linear group) and 181 patients received endoventricular patch plasty technique (patch plasty group). Ejection fraction, left ventricular systolic and end diastolic volume and left ventricular systolic and end diastolic volume index were recorded preoperatively, 2-week, 3-month, 1-year and 5-year after operation. The survival curves were plotted with Kaplan-Meier method and the survival rates were compared by Log-rank test. Results: All patients underwent surgery with a mean cardiopulmonay bypass duration of (92±32) minutes (44 to 196 minutes) and aortic cross clamp duration of (67±22) minutes (33 to 152 minutes).There were 9 perioperative deaths with a mortality rate of 3.5%. Angina pectoris of other cases are relief and heart function improved greatly. Five years after operation, the percentage of cardiac function (New Yord Heart Association) class Ⅲ to Ⅳ patients decreased from 96.1%(244/254) to 9.9%(16/161). There was no significant difference in survival rate between linear group and patch plasty group at 1-, 3-, 5-years postoperatively (96%, 91%, 77% vs. 96%, 90%, 79%, P=0.562). Ejection fraction increased from (39±10)% (range: 22% to 50%) preoperatively to (46±6)% (range: 39% to 54%) 1-year postoperatively in the linear group, while increased from (38±13)% (range: 26% to 51%) preoperatively to (50±6)% (range: 39% to 55%) in the patch plasty group. Conclusions: Left ventricular reconstruction is quite effective for patients with post-infarction left ventricular aneurysm. The choice of operative approaches is determined by the size and range of ventricular aneurysm. Both linear reconstruction and endoventricular patch plasty technique can got similarly surgical outcomes with near and late curative effect.

[Application effects of enhanced computed tomography and three-dimensional reconstruction technology in reconstruction of pediatric post-burn scars with expanded flaps]

Objective: To explore the application effects of enhanced computed tomography (CT) and three-dimensional reconstruction technology in the reconstruction of pediatric post-burn scars with expanded flaps. Methods: From May 2016 to March 2019, 19 children with hypertrophic scars after thermal injuries were admitted to our unit, including 10 boys and 9 girls, aged from 4 years and 5 months to 15 years and 11 months. The area of scars ranged from 5 cm×4 cm to 23 cm×9 cm. One or more skin and soft tissue expanders with suitable volume and shape were implanted into the normal skin area around scar of children. Three to six months later, enhanced CT and three-dimensional reconstruction were performed before the second stage operation to obtain three-dimensional images of the vascular branches in the donor site for expanded flaps to be cut, so as to determine the course and distribution of the vascular branches and guide the design of expanded flaps. According to the design scheme, the resection of scar, removal of expanders, and excision and transfer of flaps were performed to repair the wounds after scar resection. The area of flaps ranged from 6 cm×4 cm to 25 cm×10 cm. The donor site was closed directly. The number of flaps was counted. The anatomical structure, vascular distribution, and adverse reactions during enhanced CT and three-dimensional reconstruction of site for expanded flaps to be cut, the survival of expanded flaps and the follow-up after the second-stage operation were observed. Results: A total of 48 expanded flaps were designed and excised in 19 children. The anatomical structure of the site for expanded flaps to be cut and the adjacent spatial position relationship were visually observed through the three-dimensional reconstruction after enhanced CT, and no adverse reactions were observed. Arterial branch blood supply or venous return was observed in 29 sites for expanded flaps to be cut. All the expanded flaps survived well without blood supply disorder after the second stage operation. The children were followed up for 6 months to 1 year and 6 months after the second stage operation. The appearance of the flaps was natural, and the color and thickness of the flaps were similar to those of the surrounding normal skin, except for one child with obvious linear scar. Conclusions: Enhanced CT and three-dimensional reconstruction can assist the vascular assessment of the expended flaps, which is helpful for rational design of the flap excision and transfer protocol to improve the survival rate of flaps. Thus, it has certain clinical application value in the reconstruction of post-burn scar in children with expanded flaps.

[Scar management strategy in children]

Children are a special group, which have unique physiological characteristics and are still in the period of physical and mental growth and development, thus the prevention and treatment of scar in children are different from that in adults. Scar management in children is a complex and multifaceted system engineering. The grade of scar in children needs to be adjusted according to the age, period, and severity. Corresponding method needs to be chosen for the treatment of scar in children according to the classification of the scar. The compliance of children is poor, and the key to scar treatment is the persistence and cooperation of the parents, so doctors should strengthen propaganda and education to the parents of children with scar. For children with scar, individualized and comprehensive treatment should be used according to the characteristics of children to achieve good results.

The relationship of plasma fibrinogen with clinicopathological stages and tumor markers in patients with non-small cell lung cancer

Numerous studies have shown that the blood of cancer patients are generally in hypercoagulable statement. The aim of the present research is to study the relationships of plasma fibrinogen (Fbg) levels with clinicopathological stages (CS) and tumor markers of non-small cell lung cancer (NSCLC).Baseline information, plasma Fbg levels, CS, and expression level of tumor markers were collected from medical records retrospectively. Unitary linear regression was used to analyze the relationships between continuous variables and Fbg, and multiple linear regression was used to analyze the relationships between categorical variables and Fbg. National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology (Version 4) for NSCLC were adopted to evaluate CS.A total of 652 NSCLC patients were included. Compared with the females, male patients had higher mean plasma Fbg levels (P < .001). The later the N stages (P = .002), M stages (P = .002), and CS (P = .001) were, the higher the average plasma Fbg levels were. The levels of squamous cell carcinoma antigen (P = .001), carbohydrate antigen 125 (P = .041), and neuron-specific enolase (P < .001) were positively correlated with plasma Fbg concentration. The plasma level of Fbg in lung adenocarcinoma patients (P < .001) was the lowest, while that of lung squamous cell carcinoma patients (P < .001) was the highest in NSCLC patients.The plasma Fbg concentration is related to gender, CS, and tumor markers in patients with NSCLC.

Chromosomal polymorphism of mandarin vole, Microtus mandarinus (Rodentia)

The mitotic and meiotic chromosomes of mandarin vole, Microtus mandarinus Milne-Edwards, from Shandong Province of China were analyzed by conventional, G- and C-banding and Silver-staining techniques. We detected chromosomal polymorphism in the vole, exhibiting diploid chromosome numbers 2n = 48-50 and variable morphology of the 1st pair, one medium sized telocentric pair and the X chromosomes. Four types of karyotypes were revealed in the population. According to banding analysis, there were pericentric inversion, Robertsonian fusion and translocation in M. mandarinus karyotype evolution. The X displayed two different morphologies, which could be explained by prericentric inversion and a telocentric autosome translocation.

Preparation of levoglucosan by pyrolysis of cellulose and its citric acid fermentation

Levoglucosan (LG), 1,6-anhydro-beta-D-glucopyranose, was produced by pyrolysis of cellulose. A response surface method was used to optimize the reaction parameters: X1, temperature; X2, time required for heating cellulose from room temperature to the designed pyrolysis temperature; and X3, vacuum, and a Box-Behnken design was employed for this purpose. The optimal temperature and time were found to be 388 degrees C and 26.2 min by fixing the vacuum at 1 mm Hg. The levoglucosan prepared was fermented to citric acid by Aspergillus niger CBX-209, which was a mutant derived by gamma-ray mutagenesis of the parent strain CBX-2. The mutant could produce increasing citric acid with increasing LG purity and had a citric acid yield of 87.5% when using purified levoglucosan as the sole carbon source in a 5 day fermentation period.

FtsY binds to the Escherichia coli inner membrane via interactions with phosphatidylethanolamine and membrane proteins

Targeting of many polytopic proteins to the inner membrane of prokaryotes occurs via an essential signal recognition particle-like pathway. FtsY, the Escherichia coli homolog of the eukaryotic signal recognition particle receptor alpha-subunit, binds to membranes via its amino-terminal AN domain. We demonstrate that FtsY assembles on membranes via interactions with phosphatidylethanolamine and with a trypsin-sensitive component. Both interactions are mediated by the AN domain of FtsY. In the absence of phosphatidylethanolamine, the trypsin-sensitive component is sufficient for binding and function of FtsY in the targeting of membrane proteins. We propose a two-step mechanism for the assembly of FtsY on the membrane similar to that of SecA on the E. coli inner membrane.

Ancestral origins and worldwide distribution of the PRNP 200K mutation causing familial Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD) belongs to a group of prion diseases that may be infectious, sporadic, or hereditary. The 200K point mutation in the PRNP gene is the most frequent cause of hereditary CJD, accounting for >70% of families with CJD worldwide. Prevalence of the 200K variant of familial CJD is especially high in Slovakia, Chile, and Italy, and among populations of Libyan and Tunisian Jews. To study ancestral origins of the 200K mutation-associated chromosomes, we selected microsatellite markers flanking the PRNP gene on chromosome 20p12-pter and an intragenic single-nucleotide polymorphism at the PRNP codon 129. Haplotypes were constructed for 62 CJD families originating from 11 world populations. The results show that Libyan, Tunisian, Italian, Chilean, and Spanish families share a major haplotype, suggesting that the 200K mutation may have originated from a single mutational event, perhaps in Spain, and spread to all these populations with Sephardic migrants expelled from Spain in the Middle Ages. Slovakian families and a family of Polish origin show another unique haplotype. The haplotypes in families from Germany, Sicily, Austria, and Japan are different from the Mediterranean or eastern European haplotypes. On the basis of this study, we conclude that founder effect and independent mutational events are responsible for the current geographic distribution of hereditary CJD associated with the 200K mutation.

SecA is required for the insertion of inner membrane proteins targeted by the Escherichia coli signal recognition particle

Recent work has demonstrated that the signal recognition particle (SRP) is required for the efficient insertion of many proteins into the Escherichia coli inner membrane (IM). Based on an analogy to eukaryotic SRP, it is likely that bacterial SRP binds to inner membrane proteins (IMPs) co-translationally and then targets them to protein transport channels ("translocons"). Here we present evidence that SecA, which has previously been shown to facilitate the export of proteins targeted in a post-translational fashion, is also required for the membrane insertion of proteins targeted by SRP. The introduction of SecA mutations into strains that have modest SRP deficiencies produced a synthetic lethal effect, suggesting that SecA and SRP might function in the same biochemical pathway. Consistent with this explanation, depletion of SecA by inactivating a temperature-sensitive amber suppressor in a secAam strain completely blocked the membrane insertion of AcrB, a protein that is targeted by SRP. In the absence of substantial SecA, pulse-labeled AcrB was retained in the cytoplasm even after a prolonged chase period and was eventually degraded. Although protein export was also severely impaired by SecA depletion, the observation that more than 20% of the OmpA molecules were translocated properly showed that translocons were still active. Taken together, these results imply that SecA plays a much broader role in the transport of proteins across the E. coli IM than has been previously recognized.

Roles of histidine-103 and tyrosine-235 in the function of the prolipoprotein diacylglyceryl transferase of Escherichia coli

Phosphatidylglycerol:prolipoprotein diacylglyceryl transferase (Lgt) is the first enzyme in the posttranslational sequence of reactions resulting in the lipid modification of lipoproteins in bacteria. A previous comparison of the primary sequences of the Lgt enzymes from phylogenetically distant bacterial species revealed several highly conserved amino acid sequences throughout the molecule; the most extensive of these was the region 103HGGLIG108 in the Escherichia coli Lgt (H.-Y. Qi, K. Sankaran, K. Gan, and H. C. Wu, J. Bacteriol. 177:6820-6824, 1995). These studies also revealed that the kinetics of inactivation of E. coli Lgt with diethylpyrocarbonate were consistent with the modification of a single essential histidine or tyrosine residue. The current study was conducted in an attempt to identify this essential amino acid residue in order to further define structure-function relationships in Lgt. Accordingly, all of the histidine residues and seven of the tyrosine residues of E. coli Lgt were altered by site-directed mutagenesis, and the in vitro activities of the altered enzymes, as well the abilities of the respective mutant lgt alleles to complement the temperature-sensitive phenotype of E. coli SK634 defective in Lgt activity, were determined. The data obtained from these studies, in conjunction with additional chemical inactivation studies, support the conclusion that His-103 is essential for Lgt activity. These studies also indicated that Tyr-235 plays an important role in the function of this enzyme. Although other histidine and tyrosine residues were not found to be essential for Lgt activity, alterations of His-196 resulted in a significant reduction of in vitro activity.

Structure-function relationship of bacterial prolipoprotein diacylglyceryl transferase: functionally significant conserved regions

The structure-function relationship of bacterial prolipoprotein diacylgyceryl transferase (LGT) Has been investigated by a comparison of the primary structures of this enzyme in phylogenetically distant bacterial species, analysis of the sequences of mutant enzymes, and specific chemical modification of the Escherichia coli enzyme. A clone containing the gene for LGT, lgt, of the gram-positive species Staphylococcus aureus was isolated by complementation of the temperature-sensitive lgt mutant of E. coli (strain SK634) defective in LGT activity. In vivo and in vitro assays for prolipoprotein diacylglyceryl modification activity indicated that the complementing clone restored the prolipoprotein modification activity in the mutant strain. Sequence determination of the insert DNA revealed an open reading frame of 837 bp encoding a protein of 279 amino acids with a calculated molecular mass of 31.6 kDa. S. aureus LGT showed 24% identity and 47% similarity with E. coli, Salmonella typhimurium, and Haemophilus influenzae LGT.S. aureus LGT, while 12 amino acids shorter than the E. coli enzyme, had a hydropathic profile and a predicted pI (10.4) similar to those of the E. coli enzyme. Multiple sequence alignment among E. coli, S. typhimurium, H. influenzae, and S. aureus LGT proteins revealed regions of highly conserved amino acid sequences throughout the molecule. Three independent lgt mutant alleles from E. coli SK634, SK635, and SK636 and one lgt allele from S. typhimurium SE5221, all defective in LGT activity at the nonpermissive temperature, were cloned by PCR and sequenced. The mutant alleles were found to contain a single base alteration resulting in the substitution of a conserved amino acid. The longest set of identical amino acids without any gap was H-103-GGLIG-108 in LGT from these four microorganisms. In E. coli lgt mutant SK634, Gly-104 in this region was mutated to Ser, and the mutant organism was temperature sensitive in growth and exhibited low LGT activity in vitro. Diethylpyrocarbonate inactivated the E. coli LGT with a second-order rate constant of 18.6 M-1S-1, and the inactivation of LGT activity was reversed by hydroxylamine at pH 7. The inactivation kinetics were consistent with the modification of a single residue, His or Tyr, essential for LGT activity.

Mutation in Cys662 of Escherichia coli DNA topoisomerase I confers temperature sensitivity and change in DNA cleavage selectivity

Cys662 is one of the 12 cysteine residues proposed to be co-ordination sites for binding of three Zn(II) in Escherichia coli DNA topoisomerase I. Oligonucleotide-directed mutagenesis was used to convert Cys662 to either serine or histidine. The mutant enzymes were overexpressed and purified to homogeneity. Analysis of the purified enzymes demonstrated that the mutations resulted in loss of one tightly bound Zn(II). In vivo complementation tests and in vitro relaxation activity assays at different temperatures showed that the partial relaxation activities retained in the two mutant enzymes were temperature sensitive. Fluorescence measurements indicated that the wild-type and mutant enzymes have structural differences. When DNA cleavage specificity was examined, the mutant enzymes were found to have altered cleavage site preferences. The preferred cleavage sites of the wild-type enzyme all had a cytosine residue four nucleotides to the minus side of the break. The cleavage sites produced by the mutant enzymes did not show a preference for cytosine at that position.

Protein, cDNA, and genomic DNA sequences of the towel gourd trypsin inhibitor. A squash family inhibitor

Two trypsin inhibitor components of the squash family were isolated and purified from the juice of the towel gourd (Luffa cylindrica) using anhydrotrypsin affinity chromatography followed by high pressure liquid chromatography. The inhibitors were sequenced and found to consist of 28 and 29 amino acid residues. The determined sequences show high similarity to other inhibitors of the squash family, especially in the location of disulfide bonds and the reactive site and also in the COOH-terminal region. A cDNA library of towel gourd was constructed and used as a template for polymerase chain reaction amplification of two cDNA fragments of the inhibitor with an overlapping sequence. A full-length cDNA sequence coding for the inhibitor was then completed. The open reading frame codes for a prepro-inhibitor protein with the pre- and pro-peptides consisting of 21 and 13 residues, respectively. The deduced amino acid sequence of 29 residues for the inhibitor is consistent with that determined by primary structure analysis. The genomic sequence of the mature inhibitor was also ascertained using the total DNA of the towel gourd as a polymerase chain reaction template. The genomic sequence is completely identical with that of the cDNA, showing no intervening sequence.

Chemical characterization of the purified component of specific transfer factor in the leukocyte dialysates from HSV-1 immunized goats

The chemical characterization of the purified component responsible for HSV-1 specific transfer factor activity (PTFC) by high resolution analytical methods was performed. PTFC had a molecular weight of 6,000 dalton by the size-exclusion HPLC analysis; it showed a marked UV-absorbance spot at 254 nm and a fluorescent spot at 366 nm on the thin-layer plate by thin-layer chromatography which spots coincided at the same place of the plate. The amino acid composition and sequencing analyses showed that PTFC consisted of at least twelve different amino acids, but the amino acid sequence could not be determined. The combined results indicate that PTFC is a compound with a molecular weight of 6,000 dalton, composed of peptide and nucleotide-like material. The peptide is rich in aspartic acid and its N-terminal end may be blocked.

Isolation and purification of HSV-1 specific transfer factor produced by HSV-1 immunized goat leukocyte dialysate

A herpes simplex virus type 1 (HSV-1)-specific transfer factor (TF), was separated and purified from the leukocyte dialysate of goats immunized with HSV-1 using affinity chromatography on antigen-sorbent and reversed phase high performance liquid chromatography (RP-HPLC). The antigen-specific activities of the starting dialysate and the isolated TF component (s) were examined by 51Cr-labelled leukocyte adherence inhibition (51Cr LAI) assay. The analytical hydrophobic interaction HPLC (HI-HPLC) and isoelectric focusing (IEF) techniques were employed to evaluate the purity and the isoelectric point (PI) of isolated TF component(s). The experiments provided a two-step procedure for purifying the TF material from the starting dialysate. It seems that the purified active TF component (PTFC) was specific for HSV-1. The specific PTFC activity was increased 10,000-fold as compared with the activity of the dialysate. The active moiety appeared as a single band in the IEF gel as demonstrated by silver staining; it was hydrophilic and its PI was pH 4.48.