Solution properties of Escherichia coli-expressed VH domain of anti-neuraminidase antibody NC41

The VH domain of anti-influenza neuraminidase antibody NC41, with and without a C-terminal hydrophilic marker peptide (FLAG), has been expressed in high yield (15-27 mg/L) in Escherichia coli. Both forms were secreted into the periplasm where they formed insoluble aggregates which were solubilized quantitatively with 2 M guanidine hydrochloride and purified to homogeneity by ion-exchange chromatography. The VH-FLAG was composed of three isoforms (pI values of approximately 4.6, 4.9, and 5.3) and the VH molecule was composed of two isoforms with pI values of 5.1 and 6.7; the difference between the VH isoforms was shown to be due to cyclization of the N-terminal glutamine residue in the pI 5.1 isoform. At 20 degrees C and concentrations of 5-10 mg/ml the VH domain dimerized in solution and then partly precipitated, resulting in the broadening of resonances in its 1H NMR spectrum. Reagents such as CHAPS, n-ocytylglucoside, and ethylene glycol, which presumably mask the exposed hydrophobic interface of the VH molecule, prevented dimerization of the VH and permitted good-quality NMR spectra on isotope-labeled protein to be obtained.

Properties of the extracellular acidic proteases of Dichelobacter nodosus. Stability and specificity of peptide bond cleavage

Dichelobacter nodosus, a Gram negative obligate anaerobe and causative organism of ovine footrot, secretes a family of extracellular acidic serine proteases with pI's in the range of 5.2 to 5.6, and a basic serine protease with a pI of approximately 9.5. The acidic proteases show optimum activity at pH 8 and require a divalent metal ion (eg. Ca) to maintain structural integrity. In the presence of EDTA or conditions that cause protein unfolding, the proteases undergo rapid and complete autolysis. The proteases were stable to heating to about 50 degrees C for 30 min but at higher temperatures, activity was rapidly lost; virulent proteases V1 and V2 were slightly more stable (by about 5 degrees C) than benign proteases B2 and B3. The effect of various protease inhibitors on the D. nodosus acidic proteases was the same except that the inhibitor, chymostatin, markedly inhibited protease V5 but not proteases V1-3 or B1-B4. Cleavage of the oxidized insulin B-chain showed that the specificity of proteases V1-V3 and B1-B4 was identical but that it was distinct from that of proteases V5/B5.

Purification of the extracellular acidic proteases of Dichelobacter nodosus

Dichelobacter nodosus, a Gram negative obligate anaerobe and causative organism of ovine footrot, secretes a family of extracellular acidic serine proteases with pI's in the range of 5.2 to 5.6, and a basic serine protease with a pI of approximately 9.5. Four acidic proteases (V1, V2, V3 and V5) from virulent and five acidic proteases (B1 to B5) from benign strains of D. nodosus were purified by chromatography on Sephadex G-100 and DEAE-Sepharose CL-6B. Proteases V2, V5 and B5 were found to yield two forms (a and b) on purification which probably arise from limited autolysis of the parent molecule. Amino acid compositions, peptide profiles produced on autolysis and apparent Mr on SDS-PAGE of proteases V1-V3 showed that they were similar to each other and to proteases B1 to B4, and that these proteases were clearly distinct from proteases V5 and B5, which were found to be identical.

Expression in Escherichia coli of the extracellular basic protease from Dichelobacter nodosus

Dichelobacter nodosus, a Gram-negative obligate anaerobe and the causative agent of ovine footrot, secretes a number of extracellular proteases, one of which is highly basic in nature. The gene (bprV) encoding this basic protease, from virulent strain 198, has been cloned and sequenced. Clone pBR3KB contained the complete bprV gene which constitutively expressed an active protease using its own promoter, when cloned in Escherichia coli. However, levels of protease expression were low and unstable when the clone was expressed in liquid culture. A range of E. coli strains were examined for stable expression; strains NH274 and SURE were found to be better hosts for stable expression than other commonly used E. coli host strains. Stabilization and enhancement of expression was achieved by deletion of the native promoter region and expression from plasmid promoter or promoters, and by modification of culture conditions. The recombinant protease obtained from E. coli was indistinguishable from the native enzyme in size, activity, isoelectric point and immunological properties.

Characterization of a basic serine proteinase (pI approximately 9.5) secreted by virulent strains of Dichelobacter nodosus and identification of a distinct, but closely related, proteinase secreted by benign strains

An extracellular serine proteinase with a PI approximately 9.5 (referred to as 'basic proteinase') was purified to homogeneity, from strains of Dichelobacter nodosus that cause virulent foot-rot, by gel filtration of concentrated culture supernatant on Sephadex G-100 and chromatography on sulphopropyl-Sephadex C-25 at pH 8.6 D. nodosus strains that cause benign foot-rot do not secrete a corresponding basic proteinase with a pI of approximately 9.5. Benign strains secrete a closely related, but distinct, proteinase which has the same molecular mass and N-terminal sequences as the 'virulent' basic proteinase, but a lower pI of approximately 8.6. The basic proteinases from both strains appear to interact with other proteins present in the culture medium, which results in anomalous behavior on gel filtration. Pure D. nodosus 'virulent' basic proteinase has a molecular mass of 36 kDa and showed a low solubility at I < 0.05 precipitating quantitatively from solution as microcrystals. The proteinase shows optimal activity at pH 8.0 and is stable to heating to 55 degrees C for 30 min, but at higher temperatures activity is rapidly lost. Bivalent-metal ions (e.g. Ca2+) are required to maintain the structural integrity and stability of the proteinase; in the presence of EDTA or conditions that cause protein unfolding, the proteinase undergoes rapid and complete autolysis. Cleavage of oxidized insulin A- and B-chain showed that the basic proteinase has a broad specificity, including cleavage at lysine and arginine bonds.

Recombinant anti-sialidase single-chain variable fragment antibody. Characterization, formation of dimer and higher-molecular-mass multimers and the solution of the crystal structure of the single-chain variable fragment/sialidase complex

The single-chain antibody variable fragment (scFv), with a 15-residue polypeptide linker (Gly4Ser)3, of monoclonal antibody NC10 was expressed in Escherichia coli and purified to homogeneity. This scFv molecule, refolded from 6 M guanidine hydrochloride, was predominantly a monomer of 27 kDa and was stable on storage at 4 degrees and 20 degrees C. At higher protein concentrations (approximately 5 mg/ml) dimer and higher-molecular-mass multimers were formed and freezing enhanced this aggregation. The dimer was not stable and dissociated to monomer at 20 degrees C with a half-life of approximately 8 days. The higher-molecular-mass multimers and dimer dissociated to monomer in 60% ethylene glycol. Both the monomer and dimer were active and with tern N9 sialidase yielded complexes of 276 kDa and 569 kDa, respectively, indicating that four scFv molecules bound/sialidase tetramer and that the dimer was bivalent and cross-linked two sialidase tetramers. Binding studies at low concentrations and using radiolabelled scFv indicated that the binding affinity of the dimer was approximately twofold higher than that of the monomer, and the binding affinities of the scFv were similar to that of the parent NC10 antigen-binding fragment (Fab) molecule. A complex between tern N9 sialidase and NC10 scFv was crystallized and the structure of the complex was solved at 0.3-nm resolution by X-ray diffraction. Comparison of this scFv/sialidase structure with the parent Fab/sialidase structure revealed that the modes of attachment of scFv and Fab to sialidase were very similar. There was no discernible electron density for the peptide linker joining the variable heavy (VH) and variable light (VL) chains. A close interaction between two symmetry-related scFv suggests that they may have crystallized as dimers.

Cloning, sequence and expression of the gene (aprV5) encoding extracellular serine acidic protease V5 from Dichelobacter nodosus

The acidic protease V5-encoding gene (aprV5) from Gram- Dichelobacter nodosus virulent strain 198 was isolated from a cosmid bank by activity screening and sequenced. The 2371-bp nucleotide (nt) sequence contained an open reading frame coding for a protein precursor of 595 amino acid (aa) residues composed of a signal peptide, a pro-region, a mature active protease of 347 aa and a C-terminal extension region of 120 aa. The deduced aa sequence of the pre-pro-mature protease regions showed about 65% similarity to that of D. nodosus basic protease while the C-terminal extension region showed only about 26% similarity. The aprV5 gene, without its C-terminal extension region, was cloned and expressed in Escherichia coli. The acidic protease B5-encoding gene (aprB5) from non-virulent strain 305 was also cloned and sequenced. The aprB5 nt sequence showed 99% homology to that of aprV5 with two single-aa changes occurring in the precursor.

Determination of relative binding affinity of influenza virus N9 sialidases with the Fab fragment of monoclonal antibody NC41 using biosensor technology

The relative binding affinities of influenza virus N9 sialidase from term and whale with the Fab fragment of monoclonal antibody NC41 were determined using biosensor technology (Pharmacia BIAcoreTM). The apparent association and dissociation rate constants were measured in real time for the interaction of the Fab with both sialidases, the Fab being immobilised on the sensor surface. Although three-dimensional structural studies have shown that there are no apparent structural differences between the term and whale N9 sialidase epitopes to which the NC41 Fab binds, the apparent binding constant for the interaction with tern N9 sialidase was approximately 2.4-fold higher than that with whale N9 sialidase. The kinetic analysis showed that the association rate constant for the binding of whale N9 sialidase was higher than that for tern N9 sialidase (12.0 x 10(4) M-1 s-1 compared to 4.3 x 10(4) M-1 s-1) and the dissociation rate constants for the whale N9-sialidase-Fab complex were approximately 6-fold higher than for the tern N9-sialidase-Fab complex. Furthermore, kinetic analysis of the dissociation reaction showed that it was composed of two stages, an initial, faster rate followed by a late, slower rate. The values of the relative affinity constants calculated using the initial dissociation rate constant were similar to the values measured at equilibrium in the BIAcore and those determined in true solution equilibrium studies using sedimentation equilibrium. The late, slower, dissociation rate constant yielded affinity constants significantly higher than those obtained by true solution methods.

Use of a gram- signal peptide for protein secretion by gram+ hosts: basic protease of Dichelobacter nodosus is produced and secreted by Bacillus subtilis

The bprV gene, encoding the extracellular basic protease of the Gram- anaerobic bacterium Dichelobacter nodosus, was expressed and the protein secreted in Bacillus subtilis using the novel cloning/expression vector pNC3 [Wu et al., Gene 106 (1991) 103-107]. The pre- and pro-peptides were processed correctly in this heterologous system, and the 127-amino acid C-terminal extension region was also removed. The recombinant gene product was indistinguishable biochemically or immunochemically from the authentic protease and was able to form crystals upon dialysis, as was found for the authentic protease. This is the first example of the direct secretion of a Gram- extracellular enzyme in B. subtilis via its own signal peptide. The fact that this gene can be expressed and its product secreted in both Escherichia coli and B. subtilis provides a unique opportunity to study and compare the similarities and differences in protein secretion between Gram- and Gram+ organisms.

Characterisation of the wheat Mr 15000 "grain-softness protein" and analysis of the relationship between its accumulation in the whole seed and grain softness

The Mr 15000 protein associated with water-washed wheat starch granules from soft wheats was shown to be heterogeneous: it could be divided into a fraction containing one or moreα-amylase inhibitor subunits and a fraction largely composed of a previously uncharacterised polypeptide(s) referred to as the "grainsoftness protein" (GSP). The major N-terminal sequence and sequences of peptides derived from protease digests of GSP are reported. An antiserum specific for GSP was used to show that GSP accumulated in both hard and soft wheat grains, but the GSP in soft grains associated more strongly with starch granules than the GSP in hard grains. A positive correlation between grain softness and accumulation of GSP in the seed was demonstrated for a range of cultivars. This differs from the qualitative relationship, based on the isolated starch fraction, between GSP and grain softness that has already been reported. Analysis of wholemeal extracts with the antiserum demonstrated that the accumulation of GSP in the seed was dependent on the short arm of chromosome 5D, which also encodes theHa locus. In addition, examination of near-isogenic lines differing in hardness indicated that the gene(s) controlling GSP was (were) linked with theHa locus. The findings indicate that GSP may be the product of theHa locus and thus be the major factor that determines the milling characteristics of bread wheats.

Recombinant antineuraminidase single chain antibody: expression, characterization, and crystallization in complex with antigen

The variable heavy (VH) and variable light (VL) genes of NC10, a monoclonal antibody with specificity toward N9 neuraminidase (NA), were cloned and sequenced. A single chain Fv (scFv) fragment of NC10, consisting of VH and VL domains joined by a peptide linker, was designed, constructed and expressed in the E. coli expression vector pPOW. The N-terminal secretion signal PelB directed the synthesized protein into the periplasm where it was associated with the insoluble membrane fraction. An octapeptide (FLAG) tail was fused to the C-terminus of the single chain Fv to aid in its detection and remained intact throughout the protein purification process. NC10 scFv was purified by solubilization of the E. coli membrane fraction with guanidinium hydrochloride followed by column chromatography. The purified NC10 scFv showed binding affinity for its antigen, NA, 2-fold lower than that of the parent Fab. The complex between NA and the scFv has been crystallized by the vapor diffusion method. The crystals are tetragonal, space group P42(1)2, with unit cell dimensions a = b = 141 A, c = 218 A.

Amino acid sequence of extracellular acidic protease V5 of Dichelobacter nodosus, the causative organism of ovine footrot

Dichelobacter nodosus, a Gram-negative obligate anaerobe and the causative organism of ovine footrot, secretes a family of extracellular serine proteases with pI's in the range of 5.2 to 5.6 and a serine basic protease with a pI of approximately 9.5. The primary structure of acidic protease V5 (pI approximately 5.2) from D. nodosus virulent strain 198 was determined by direct amino acid sequencing. This protease consists of a single polypeptide chain of 347 amino acids, contains two disulfide bonds and has a M(r) of 35960. Comparison of the D. nodosus acidic protease V5 sequence with that of other serine proteases showed that it is a member of the subtilisin family of proteases with strong conservation of identity around the catalytic residues. The sequence of protease V5 showed 64% identity to D. nodosus basic protease (pI approximately 9.5) and 53% identity to the extracellular serine protease of Xanthomonas campestris, a plant pathogen but only 25-35% identity to other proteases of the subtilisin family. The D. nodosus proteases are similar in length to X. campestris protease (but some 70 residues shorter than the subtilisins) and they share two conserved disulfide bonds with the X. campestris protease, a feature not observed for other members of the subtilisin family.

Amino acid and DNA sequences of an extracellular basic protease of Dichelobacter nodosus show that it is a member of the subtilisin family of proteases

A DNA fragment encoding an extracellular basic protease (pI approximately 9.5) from Dichelobacter nodosus, a Gram-negative obligate anaerobe and the causative agent of ovine footrot, has been cloned and expressed in Escherichia coli and sequenced. E. coli harbouring a plasmid with a 3-kb DNA fragment containing the D. nodosus basic-protease gene exhibited proteolytic activity when tested on skim-milk plates. The sequence of the native basic protease isolated from D. nodosus was also determined by direct amino acid sequencing. Comparison of the deduced sequence of the primary translation product (603 residues) and that of the native protease (344 residues) indicates that the protease is synthesized as a precursor molecule, containing a signal peptide (21 residues), a 111 amino acid pro-peptide and a 127 residue C-terminal extension which is subsequently processed to the mature active form. Comparison of the D. nodosus basic protease sequence with that of other serine proteases showed that it is related to the subtilisin family of proteases with strong conservation of sequence identity around the catalytic site residues. A remarkable similarity in structure was found to the serine protease of Xanthomonas campestris, a plant pathogen, with respect to the length of the precursor segments, conservation of disulfide bridges and approximately 50% sequence identity of the mature proteases.

The structure of the complex between influenza virus neuraminidase and sialic acid, the viral receptor

Crystallographic studies of neuraminidase-sialic acid complexes indicate that sialic acid is distorted on binding the enzyme. Three arginine residues on the enzyme interact with the carboxylate group of the sugar which is observed to be equatorial to the saccharide ring as a consequence of its distorted geometry. The glycosidic oxygen is positioned within hydrogen-bonding distance of Asp-151, implicating this residue in catalysis.

High-level temperature-induced synthesis of an antibody VH-domain in Escherichia coli using the PelB secretion signal

We have constructed a temperature-inducible Escherichia coli expression vector (pPOW) for enhanced secretion of antibody (Ab) domains and other foreign proteins. The vector contains the lambda pRpL promoters in tandem, and the cI857 gene encoding the temperature-sensitive repressor which provide tight control over protein production. The PelB secretion signal directs the synthesized foreign protein through the cytoplasmic membrane. A mouse Ab fragment (the variable heavy (VH) domain of NC41) was synthesized efficiently by this vector and accumulated with the cell membranes (not as inclusion bodies) at levels of 30 mg/l. This represents the highest yields reported to date for Ab fragments with a native N terminus. An octapeptide (FLAG) tail was fused to the C terminus of the VH domain to aid in purification, and remained intact throughout the protein purification process. The optimum conditions for protein production were controlled by the type of culture medium used, the age of the bacterial population at the time of induction, and the period of synthesis of the protein product. The purified Ab VH fragment showed binding affinity (Ka less than 10(4)/M) to its target antigen (neuraminidase).

Primary structure of Kunitz-type trypsin inhibitor-2a (pI 5.9) from Psophocarpus tetragonolobus (L.) DC seed

The primary structure of acidic trypsin inhibitor-2a (WBTI-2a, pI 5.9) from Psophocarpus tetragonolobus (L.) DC seed was determined. This inhibitor consists of a single polypeptide chain of 180 amino acids including four half-cystine residues and has an N-terminal residue of pyroglutamic acid. The sequence of WBTI-2a, pI 5.9, showed 84% identity to acidic trypsin inhibitor-2 (WBTI-2, pI 5.1) but only 57% identity to the basic trypsin inhibitor (WBTI-1, pI 8.9) and 50% identity to the chymotrypsin inhibitor of winged bean. The data indicate that winged bean seed contains a family of three Kunitz-type inhibitors which have about 50% identity.

A new method for the purification of the influenza A virus neuraminidase

A rapid new method for the purification of neuraminidase (NA) heads from influenza A virus is described. Virus was pelleted directly from allantoic fluid and was digested with pronase. The cores were removed by centrifugation, redigested and the released NA heads were pooled and concentrated. The NA was separated from all contaminating proteins in a single step on a Superose 12 column. The purified material was suitable for both crystallography and for the production of monospecific antisera.

Amino acid and cDNA sequences of a methionine-rich 2S protein from sunflower seed (Helianthus annuus L.)

The amino acid sequence of a methionine-rich 2S seed protein from sunflower (Helianthus annuus L.) and the sequence of a cDNA clone which codes for the entire primary translation product have been determined. The mature protein consists of a single polypeptide chain of 103 amino acids (molecular mass 12133 Da) which contains 16 residues of methionine and 8 residues of cysteine. The cDNA sequence established that the protein is synthesized as a precursor of 141 residues with a typical hydrophobic signal sequence of 25 residues followed by a further 13-residue hydrophobic pro-sequence which is presumably removed by post-translational cleavage. The sequence of the mature protein and that deduced from the cDNA were identical with no evidence of processing at the C-terminus. Comparison of the sunflower methionine-rich protein sequence with sequences of other seed 2S proteins from dicotyledons and monocotyledons showed limited but distinct sequence similarities; in particular the arrangement of the cysteine residues was conserved. The sunflower protein shows 34% identity with the methionine-rich Brazil nut 2S protein and the prepro regions of the precursors of these two proteins show about 50% identity. This similarity indicates that these methionine-rich 2S proteins have diverged as a subclass of the 2S superfamily of proteins which contain only 2-3% methionine. While the related 2S proteins from other dicotyledons are processed to a small and large subunit, the sunflower protein is not cleaved in this way.

Amino acid sequence and disulfide bridges of affinity purified Kunitz-type chymotrypsin inhibitor from winged bean seed (Psophocarpus tetragonolobus (L.) DC)

The primary sequence of the affinity purified chymotrypsin inhibitor, WBCI, isolated from the albumin fraction of Psophocarpus tetragonolobus (L.) DC cv. UPS-122 seed was determined. The inhibitor consisted of a single polypeptide chain of 183 amino acids (Mr 20285) and the four half-cystine residues in the molecule formed two intramolecular disulfide bridges equivalent to those in other Kunitz-type seed inhibitors. The sequence of this chymotrypsin inhibitor was identical to that of chymotrypsin inhibitor-3 from cultivar UPS-31 and it showed about 50% sequence similarity to the winged bean acidic (WBTI-2, pI 5.1) and basic (WBTI-1, pI 8.9) trypsin inhibitors. Sequence similarities to other Kunitz-type seed inhibitors are discussed.

Pea convicilin: structure and primary sequence of the protein and expression of a gene in the seeds of transgenic tobacco

Convicilin, a trimeric globulin of pea (Pisum sativum L.) seeds, is closely related to vicilin and composed of polypeptides of 68.2 kilodaltons. A partial copy DNA (cDNA) clone encoding convicilin was isolated, sequenced, and used to select a convicilin gene from a pea genomic library. A part of the genomic clone was sequenced to obtain the coding sequences missing in the cDNA clone and a further 1 kilobase 5' to the start of transcription were also obtained. The entire sequence of convicilin was deduced from the combined genomic and cDNA sequences. The complete gene encoding convicilin was transferred to tobacco (Nicotiana tabacum L.) and the characteristics of its expression in the seeds of transgenic plants were studied. An unprocessed polypeptide, which was found only in the seeds of the transgenic plants, was identical in size to pea convicilin, and was recognized by vicilin antibodies. Convicilin, which does not undergo posttranslational cleavage in peas, was partially processed to polypeptides of a relative molecular mass (Mr) of approx. 50000 in transgenic tobacco seeds. There was a twofold variation in the level of convicilin accumulated by the mature seeds of a number of transgenic plants and this was well correlated with the number of gene copies incorporated in the different transformants. In the seeds of tobacco plants that contained a single copy of the transferred gene it was estimated that convicilin comprised up to 2% of the seed protein. Thus, using a combination of gene sequencing and expression in a heterologous host we believe we have characterized the gene corresponding to theCvc locus, whereas the gene described by D. Bown et al. (1988, Biochem J.,251, 717-726) probably encodes a minor convicilin-related protein.

A cDNA-based comparison of dehydration-induced proteins (dehydrins) in barley and corn

Several cDNAs related to an ABA-induced cDNA from barley aleurone were isolated from barley and corn seedlings that were undergoing dehydration. Four different barley polypeptides with sizes of 22.6, 16.2, 14.4 and 14.2 kDa and a single corn polypeptide with a size of 17.0 kDa were predicted from the nucleotide sequences of the cDNAs. These dehydration-induced proteins (dehydrins) are very similar to each other and to a previously identified rice protein induced by ABA and salt, and have at least some similarity to a previously identified cotton embryo protein. Each dehydrin is extremely hydrophilic, glycine-rich, cysteine- and tryptophan-free and contains repeated units in a conserved linear order. A lysine-rich repeating unit occurs twice in each protein, once at the carboxy terminus and once partway through the polypeptide, adjacent to a succession of serines. This repeating unit and the adjacent flanking run of serines are conserved with minimal variation among all dehydrins. Another repeating unit is flanked by the two copies of the lysine-rich unit, and varies in number from one to five copies. This latter repeating unit is less conserved than the former, varying even within a singly dehydrin. The messenger RNAs corresponding to each cDNA are abundant in dehydrating, but not in well-watered seedlings. The amino acid sequence of tryptic peptides from purified dehydration-induced proteins of corn established that the corn cDNAs correspond to a protein that is produced in abundance during the response of corn seedlings to dehydration.

Amino acid sequence of a crystalline seed albumin (winged bean albumin-1) from Psophocarpus tetragonolobus (L.) DC. Sequence similarity with Kunitz-type seed inhibitors and 7S storage globulins

The complete amino acid sequence of winged bean albumin-1 (WBA-1) of Psophocarpus tetragonolobus (L.) DC has been determined. The protein consists of a single polypeptide chain of 175 amino acid residues, with one disulfide bond, corresponding to a molecular mass of 19333 Da. WBA-1 was found to be homologous with the Kunitz-type seed trypsin inhibitors. The similarity between WBA-1 and the trypsin inhibitors from soybean and winged bean was 38% and 28%, respectively; similarity was most marked in the C-terminal third of the sequence with identities of 47% and 37%, respectively. Significant similarity was found also between the 2S Kunitz-type proteins and the carboxy-terminal region of the 7S storage globulins, suggesting that these two groups of proteins are related and may have evolved from a common ancestral precursor. Circular dichroism measurements suggest a high content of beta sheet (52%) while secondary structure predictions based on amino acid sequence indicate a similar content and distribution of beta sheet to that found for soybean trypsin inhibitor by X-ray diffraction studies.

Amino acid sequences of hemoglobins I and II from root nodules of the non-leguminous Parasponia rigida-rhizobium symbiosis, and a correction of the sequence of hemoglobin I from Parasponia andersonii

The amino acid sequence of hemoglobins I (pI 6.15 as oxyhemoglobin) and II (pI 5.64 as oxyhemoglobin) from the nitrogen-fixing root nodules of Parasponia rigida have been determined by protein sequencing. The sequence of hemoglobin I (pI 6.16, as oxyhemoglobin) from Parasponia andersonii was re-examined and the corrected primary structure, now in agreement with that predicted from the DNA sequence, is reported. The three Parasponia hemoglobins contain 161 amino acid residues (Mr approximately equal to 18,700 including the heme) with a single cysteine residue and five methionine residues. The N-terminal serine is blocked by an acetyl group. The primary structure of the Parasponia hemoglobins is highly conserved. Hemoglobins I from the two species of Parasponia are identical; both show microheterogeneity at position 30 (Asp/Glu substitution) and hemoglobin I from P. rigida shows microheterogeneity at position 150 (Ala/Val) while hemoglobin I from P. andersonii has only an Ala at 150. P. rigida hemoglobin II shows no microheterogeneity at these positions, having Asp and Val residues respectively, and it contains a single amino acid change of a Gln for an Arg at position 85, which accounts for the 0.5 unit difference in isoelectric point observed between hemoglobins I and II. The sequence data are consistent with allelic heterogeneity at a single locus rather than different genes.

Sequence and identification of the barley yellow dwarf virus coat protein gene

The nucleotide sequence of the coat protein gene of barley yellow dwarf virus (BYDV, PAV serotype) was determined, and the amino acid sequence was deduced. The open reading frame, encoding a protein of relative molecular mass (Mr) 22,047, was confirmed as the coat protein gene by comparison with amino acid sequences of tryptic peptides derived from dissociated virions. In addition, a fragment of this gene expressed in Escherichia coli produced a product which was recognized by antibodies prepared against purified BYDV virions. An overlapping reading frame encoding an Mr 17,147 protein is contained completely within the coat protein gene.

Crystallization and preliminary crystallographic data of the major albumin from Psophocarpus tetragonolobus (L.) DC

The major seed albumin from Psophocarpus tetragonolobus (L.) DC, winged bean albumin 1, has been crystallized from ethanol as rhombic needles in a form suitable for high resolution x-ray crystallographic studies. The space group is I4(1)22 with cell parameters a = b = 95.6 A, and c = 86.0 A. Amino acid sequence homology between winged bean albumin 1 and legume 7 S globulins suggests that the former may be related to a structural domain of the 7 S globulins.