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Du Y, Thanapipatsiri A, Yokoyama K. Biosynthesis and Genome Mining Potentials of Nucleoside Natural Products. Chembiochem 2023; 24:e202300342. [PMID: 37357819 PMCID: PMC10530009 DOI: 10.1002/cbic.202300342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/20/2023] [Accepted: 06/22/2023] [Indexed: 06/27/2023]
Abstract
Nucleoside natural products show diverse biological activities and serve as leads for various application purposes, including human and veterinary medicine and agriculture. Studies in the past decade revealed that these nucleosides are biosynthesized through divergent mechanisms, in which early steps of the pathways can be classified into two types (C5' oxidation and C5' radical extension), while the structural diversity is created by downstream tailoring enzymes. Based on this biosynthetic logic, we investigated the genome mining discovery potentials of these nucleosides using the two enzymes representing the two types of C5' modifications: LipL-type α-ketoglutarate (α-KG) and Fe-dependent oxygenases and NikJ-type radical S-adenosyl-L-methionine (SAM) enzymes. The results suggest that this approach allows discovery of putative nucleoside biosynthetic gene clusters (BGCs) and the prediction of the core nucleoside structures. The results also revealed the distribution of these pathways in nature and implied the possibility of future genome mining discovery of novel nucleoside natural products.
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Affiliation(s)
- Yanan Du
- Department of Biochemistry, Duke University School of Medicine, 307 Research Drive, Durham, NC 27710, USA
| | - Anyarat Thanapipatsiri
- Department of Biochemistry, Duke University School of Medicine, 307 Research Drive, Durham, NC 27710, USA
| | - Kenichi Yokoyama
- Department of Biochemistry, Duke University School of Medicine, 307 Research Drive, Durham, NC 27710, USA
- Department of Chemistry, Duke University, 307 Research Drive, Durham, NC 27710, USA
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Draelos MM, Thanapipatsiri A, Sucipto H, Yokoyama K. Cryptic phosphorylation in nucleoside natural product biosynthesis. Nat Chem Biol 2020; 17:213-221. [PMID: 33257873 PMCID: PMC7855722 DOI: 10.1038/s41589-020-00656-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 08/20/2020] [Indexed: 11/11/2022]
Abstract
Kinases are annotated in many nucleoside biosynthetic gene clusters (BGCs) but generally are considered responsible only for self-resistance. Here, we report an unexpected 2’-phosphorylation of nucleoside biosynthetic intermediates in the nikkomycin and polyoxin pathways. This phosphorylation is a unique cryptic modification as it is introduced in the third of seven steps during aminohexuronic acid (AHA) nucleoside biosynthesis, retained throughout the pathway’s duration, and is removed in the last step of the pathway. Bioinformatic analysis of reported nucleoside BGCs suggests the presence of cryptic phosphorylation in other pathways and the importance of functional characterization of kinases in nucleoside biosynthetic pathways in general. This study also functionally characterized all of the enzymes responsible for AHA biosynthesis and revealed that AHA is constructed via a unique oxidative C-C bond cleavage reaction. The results suggest a divergent biosynthetic mechanism for three classes of antifungal nucleoside natural products.
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Affiliation(s)
| | | | - Hilda Sucipto
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, USA
| | - Kenichi Yokoyama
- Department of Chemistry, Duke University, Durham, NC, USA. .,Department of Biochemistry, Duke University School of Medicine, Durham, NC, USA.
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3
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Lin CI, McCarty RM, Liu HW. The biosynthesis of nitrogen-, sulfur-, and high-carbon chain-containing sugars. Chem Soc Rev 2013; 42:4377-407. [PMID: 23348524 PMCID: PMC3641179 DOI: 10.1039/c2cs35438a] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Carbohydrates serve many structural and functional roles in biology. While the majority of monosaccharides are characterized by the chemical composition (CH2O)n, modifications including deoxygenation, C-alkylation, amination, O- and N-methylation, which are characteristic of many sugar appendages of secondary metabolites, are not uncommon. Interestingly, some sugar molecules are formed via modifications including amine oxidation, sulfur incorporation, and "high-carbon" chain attachment. Most of these unusual sugars have been identified over the past several decades as components of microbially produced natural products, although a few high-carbon sugars are also found in the lipooligosaccharides of the outer cell walls of Gram-negative bacteria. Despite their broad distribution in nature, these sugars are considered "rare" due to their relative scarcity. The biosynthetic steps that underlie their formation continue to perplex researchers to this day and many questions regarding key transformations remain unanswered. This review will focus on our current understanding of the biosynthesis of unusual sugars bearing oxidized amine substituents, thio-functional groups, and high-carbon chains.
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Affiliation(s)
| | | | - Hung-wen Liu
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712
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Oberdorfer G, Binter A, Ginj C, Macheroux P, Gruber K. Structural and functional characterization of NikO, an enolpyruvyl transferase essential in nikkomycin biosynthesis. J Biol Chem 2012; 287:31427-36. [PMID: 22810238 DOI: 10.1074/jbc.m112.352096] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nikkomycins are peptide-nucleoside compounds with fungicidal, acaricidal, and insecticidal properties because of their strong inhibition of chitin synthase. Thus, they are potential antibiotics especially for the treatment of immunosuppressed patients, for those undergoing chemotherapy, or after organ transplants. Although their chemical structure has been known for more than 30 years, only little is known about their complex biosynthesis. The genes encoding for proteins involved in the biosynthesis of the nucleoside moiety of nikkomycins are co-transcribed in the same operon, comprising the genes nikIJKLMNO. The gene product NikO was shown to belong to the family of enolpyruvyl transferases and to catalyze the transfer of an enolpyruvyl moiety from phosphoenolpyruvate to the 3'-hydroxyl group of UMP. Here, we report activity and inhibition studies of the wild-type enzyme and the variants C130A and D342A. The x-ray crystal structure revealed differences between NikO and its homologs. Furthermore, our studies led to conclusions concerning substrate binding and preference as well as to conclusions about inhibition/alkylation by the antibiotic fosfomycin.
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Affiliation(s)
- Gustav Oberdorfer
- Institute of Molecular Biosciences, University of Graz, A-8010 Graz, Austria
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Binter A, Oberdorfer G, Hofzumahaus S, Nerstheimer S, Altenbacher G, Gruber K, Macheroux P. Characterization of the PLP-dependent aminotransferase NikK from Streptomyces tendae and its putative role in nikkomycin biosynthesis. FEBS J 2011; 278:4122-35. [PMID: 21884568 DOI: 10.1111/j.1742-4658.2011.08319.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
As inhibitors of chitin synthase, nikkomycins have attracted interest as potential antibiotics. The biosynthetic pathway to these peptide nucleosides in Streptomyces tendae is only partially known. In order to elucidate the last step of the biosynthesis of the aminohexuronic building block, we have heterologously expressed a predicted aminotransferase encoded by the gene nikK from S. tendae in Escherichia coli. The purified protein, which is essential for nikkomycin biosynthesis, has a pyridoxal-5'-phosphate cofactor bound as a Schiff base to lysine 221. The enzyme possesses aminotransferase activity and uses several standard amino acids as amino group donors with a preference for glutamate (Glu > Phe > Trp > Ala > His > Met > Leu). Therefore, we propose that NikK catalyses the introduction of the amino group into the ketohexuronic acid precursor of nikkomycins. At neutral pH, the UV-visible absorbance spectrum of NikK has two absorbance maxima at 357 and 425 nm indicative of the presence of the deprotonated and protonated aldimine with an estimated pK(a) of 8.3. The rate of donor substrate deamination is faster at higher pH, indicating that an alkaline environment favours the deamination reaction.
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Affiliation(s)
- Alexandra Binter
- Graz University of Technology, Institute of Biochemistry, Graz, Austria
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Winn M, Goss RJM, Kimura KI, Bugg TDH. Antimicrobial nucleoside antibiotics targeting cell wall assembly: recent advances in structure-function studies and nucleoside biosynthesis. Nat Prod Rep 2009; 27:279-304. [PMID: 20111805 DOI: 10.1039/b816215h] [Citation(s) in RCA: 221] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The quest for new antibiotics, especially those with activity against Gram-negative bacteria, is urgent; however, very few new antibiotics have been marketed in the last 40 years, with this limited number falling into only four new structural classes. Several nucleoside natural product antibiotics target bacterial translocase MraY, involved in the lipid-linked cycle of peptidoglycan biosynthesis, and fungal chitin synthase. Biosynthetic studies on the nikkomycin, caprazamycin and pacidamycin/mureidomycin families are also reviewed.
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Affiliation(s)
- Michael Winn
- School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
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Li R, Xie Z, Tian Y, Yang H, Chen W, You D, Liu G, Deng Z, Tan H. polR, a pathway-specific transcriptional regulatory gene, positively controls polyoxin biosynthesis in Streptomyces cacaoi subsp. asoensis. MICROBIOLOGY-SGM 2009; 155:1819-1831. [PMID: 19383687 DOI: 10.1099/mic.0.028639-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The polyoxin (POL) biosynthetic gene cluster (pol) was recently cloned from Streptomyces cacaoi subsp. asoensis. A 3.3 kb DNA fragment carrying an obvious open reading frame (polR), whose deduced product shows sequence similarity to SanG of Streptomyces ansochromogenes and PimR of Streptomyces natalensis, was revealed within the pol gene cluster. Disruption of polR abolished POL production, which could be complemented by the integration of a single copy of polR into the chromosome of the non-producing mutant. The introduction of an extra copy of polR in the wild-type strain resulted in increased production of POLs. The transcription start point (tsp) of polR was determined by S1 mapping. Reverse transcriptase PCR experiments showed that PolR is required for the transcription of 18 structural genes in the pol gene cluster. Furthermore, we showed that polC and polB, the respective first genes of two putative operons (polC-polQ2 and polA-polB) consisting of 16 and 2 of these 18 genes, have similar promoter structures. Gel retardation assays indicated that PolR has specific DNA-binding activity for the promoter regions of polC and polB. Our data suggest that PolR acts in a positive manner to regulate POL production by activating the transcription of at least two putative operons in the pol gene cluster.
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Affiliation(s)
- Rui Li
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhoujie Xie
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Yuqing Tian
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Haihua Yang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Wenqing Chen
- Laboratory of Microbial Metabolism and School of Life Science and Biotechnology, Shanghai Jiaotong University, Shanghai 200030, China
| | - Delin You
- Laboratory of Microbial Metabolism and School of Life Science and Biotechnology, Shanghai Jiaotong University, Shanghai 200030, China
| | - Gang Liu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Zixin Deng
- Laboratory of Microbial Metabolism and School of Life Science and Biotechnology, Shanghai Jiaotong University, Shanghai 200030, China
| | - Huarong Tan
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
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Chen W, Huang T, He X, Meng Q, You D, Bai L, Li J, Wu M, Li R, Xie Z, Zhou H, Zhou X, Tan H, Deng Z. Characterization of the polyoxin biosynthetic gene cluster from Streptomyces cacaoi and engineered production of polyoxin H. J Biol Chem 2009; 284:10627-38. [PMID: 19233844 DOI: 10.1074/jbc.m807534200] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A gene cluster (pol) essential for the biosynthesis of polyoxin, a nucleoside antibiotic widely used for the control of phytopathogenic fungi, was cloned from Streptomyces cacaoi. A 46,066-bp region was sequenced, and 20 of 39 of the putative open reading frames were defined as necessary for polyoxin biosynthesis as evidenced by its production in a heterologous host, Streptomyces lividans TK24. The role of PolO and PolA in polyoxin synthesis was demonstrated by in vivo experiments, and their functions were unambiguously characterized as O-carbamoyltransferase and UMP-enolpyruvyltransferase, respectively, by in vitro experiments, which enabled the production of a modified compound differing slightly from that proposed earlier. These studies should provide a solid foundation for the elucidation of the molecular mechanisms for polyoxin biosynthesis, and set the stage for combinatorial biosynthesis using genes encoding different pathways for nucleoside antibiotics.
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Affiliation(s)
- Wenqing Chen
- Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiaotong University, Shanghai 200030, China
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Ginj C, Rüegger H, Amrhein N, Macheroux P. 3'-Enolpyruvyl-UMP, a novel and unexpected metabolite in nikkomycin biosynthesis. Chembiochem 2006; 6:1974-6. [PMID: 16206325 DOI: 10.1002/cbic.200500208] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Cristian Ginj
- Institut für Pflanzenwissenschaften, ETH-Zentrum, Zürich, Switzerland
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Jiang XJ, Kalman TI. Synthesis of 4-formyl-4-imidazolin-2-one nucleosides, isomers of uridine and 2'-deoxyuridine. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2004; 23:307-16. [PMID: 15043156 DOI: 10.1081/ncn-120027837] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The syntheses of the ribo- and deoxyribonucleoside derivatives of 4-formyl-4-imidazolin-2-one, isosteric isomers of uridine and 2'-deoxyuridine, respectively, were carried out by ring contraction of the corresponding 5-bromouracil nucleosides, followed by conversion of the carboxyl side-chain of the products to the respective carboxaldehyde derivatives.
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Affiliation(s)
- Xiang-Jun Jiang
- Department of Chemistry, University at Buffalo, Amherst, New York 14260, USA
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Cone MC, Yin X, Grochowski LL, Parker MR, Zabriskie TM. The blasticidin S biosynthesis gene cluster from Streptomyces griseochromogenes: sequence analysis, organization, and initial characterization. Chembiochem 2003; 4:821-8. [PMID: 12964155 DOI: 10.1002/cbic.200300583] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Blasticidin S is a potent antifungal and cytotoxic peptidyl nucleoside antibiotic from Streptomyces griseochromogenes. The mixed biosynthesis of the compound is evident from the three distinct structural components: a cytosine base, an amino deoxyglucuronic acid, and N-methyl beta-arginine. The blasticidin S biosynthesis gene cluster was cloned from S. griseochromogenes and the pathway heterologously expressed in S. lividans from a cosmid harboring a 36.7-kb fragment of S. griseochromogenes DNA. The complete DNA sequence of this insert has now been determined and evidence suggests a contiguous 20-kb section defines the blasticidin S biosynthesis cluster. The predicted functions of several open reading frames are consistent with the expected biochemistry and include an arginine 2,3-aminomutase, a cytosylglucuronic acid synthase, and a guanidino N-methyltransferase. Insight into other steps in the assembly of blasticidin S was evident from sequence homology with proteins of known function and heterologous expression of fragments of the cluster. Additionally, the gene that directs the production of free cytosine, blsM, was subcloned and expressed in Escherichia coli. Characterization of BlsM revealed that cytidine monophosphate serves as the precursor to cytosine.
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Affiliation(s)
- Martha C Cone
- Department of Pharmaceutical Sciences, Oregon State University, Corvallis, OR 97331, USA
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Tsvetanova BC, Kiemle DJ, Price NPJ. Biosynthesis of tunicamycin and metabolic origin of the 11-carbon dialdose sugar, tunicamine. J Biol Chem 2002; 277:35289-96. [PMID: 12093793 DOI: 10.1074/jbc.m201345200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tunicamycin is a reversible inhibitor of polyprenol-phosphate: N-acetylhexosamine-1-phosphate translocases and is produced by several Streptomyces species. We have examined tunicamycin biosynthesis, an important but poorly characterized biosynthetic pathway. Biosynthetic precursors have been identified by incorporating radioactive and stable isotopes, and by determining the labeling pattern using electrospray ionization-collision induced dissociation-mass spectrometry (ESI-CID-MS), and proton, deuterium, and C-13 nuclear magnetic resonance (NMR) spectroscopy. Preparation and analysis of [uracil-5-(2)H]-labeled tunicamycin established the complete ESI-CID-MS fragmentation pathway for the major components of the tunicamycin complex. Competitive metabolic experiments indicate that 7 deuteriums incorporate into tunicamycin from [6,6'-(2)H,(2)H]-labeled D-glucose, 6 of which arise from D-GlcNAc and 1 from uridine and/or D-ribose. Inverse correlation NMR experiments (heteronuclear single-quantum coherence (HSQC)) of (13)C-labeled tunicamycin enriched from D-[1-(13)C]glucose suggest that the unique tunicamine 11-carbon dialdose sugar backbone arises from a 5-carbon furanose precursor derived from uridine and a 6-carbon N-acetylamino-pyranose precursor derived from UDP-D-N-acetylglucosamine. The equivalent incorporation of (13)C into both the alpha-1" and beta-11' anomeric carbons of tunicamycin supports a direct biosynthesis via 6-carbon metabolism. It also indicates that the tunicamine motif and the alpha-1"-linked GlcNAc residue are both derived from the same metabolic pool of UDP-GlcNAc, without significant differential metabolic processing. A biosynthetic pathway is therefore proposed for tunicamycin for the first time: an initial formation of the 11-carbon tunicamine sugar motif from uridine and UDP-GlcNAc via uridine-5'-aldehyde and UDP-4-keto-6-ene-N-acetylhexosamine, respectively, and subsequent formation of the anomeric-to-anomeric alpha, beta-1",11'-glycosidic bond.
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Affiliation(s)
- Billyana C Tsvetanova
- Department of Chemistry, State University of New York, College of Environmental Science and Forestry, Syracuse, New York 13210, USA
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Chen H, Hubbard BK, O'Connor SE, Walsh CT. Formation of beta-hydroxy histidine in the biosynthesis of nikkomycin antibiotics. CHEMISTRY & BIOLOGY 2002; 9:103-12. [PMID: 11841943 DOI: 10.1016/s1074-5521(02)00090-x] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Nikkomycins, a group of peptidyl nucleoside antibiotics produced Streptomyces tendae Tü901, are potent competitive inhibitors of chitin synthase. In this study, three nikkomycin biosynthetic enzymes, NikP1, NikQ, and NikP2, were overexpressed, purified, and characterized. The NikP1 activated L-His and transferred it to the carrier protein domain to form L-His-S-NikP1, which served as the beta-hydroxylation substrate of NikQ. The beta-OH-His was then hydrolytically released from NikP1 by NikP2. The results reported here substantiate our earlier proposal that the covalent tethering of an amino acid onto a carrier protein domain prior to downstream modification is a general strategy for diverting a fraction of the amino acid into secondary metabolism.
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Affiliation(s)
- Huawei Chen
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
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Samland AK, Jelesarov I, Kuhn R, Amrhein N, Macheroux P. Thermodynamic characterization of ligand-induced conformational changes in UDP-N-acetylglucosamine enolpyruvyl transferase. Biochemistry 2001; 40:9950-6. [PMID: 11502190 DOI: 10.1021/bi0107041] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The binding of UDP-N-acetylglucosamine (UDPNAG) to the enzyme UDP-N-acetylglucosamine enolpyruvyl transferase (MurA) was studied in the absence and presence of the antibiotic fosfomycin by isothermal titration calorimetry. Fosfomycin binds covalently to MurA in the presence of UDPNAG and also in its absence as demonstrated by MALDI mass spectrometry. The covalent attachment of fosfomycin affects the thermodynamic parameters of UDPNAG binding significantly: In the absence of fosfomycin the binding of UDPNAG is enthalpically driven (DeltaH = -35.5 kJ mol(-1) at 15 degrees C) and opposed by an unfavorable entropy change (DeltaS = -25 J mol(-1) K(-1)). In the presence of covalently attached fosfomycin the binding of UDPNAG is entropically driven (DeltaS = 187 J mol(-1)K(-1) at 15 degrees C) and associated with unfavorable changes in enthalpy (DeltaH = 28.8 kJ mol(-1)). Heat capacities for UDPNAG binding in the absence or presence of fosfomycin were -1.87 and -2.74 kJ mol(-1) K(-1), respectively, indicating that most ( approximately 70%) of the conformational changes take place upon formation of the UDPNAG-MurA binary complex. The major contribution to the heat capacity of ligand binding is thought to be due to changes in the solvent-accessible surface area. However, associated conformational changes, if any, also contribute to the experimentally measured magnitude of the heat capacity. The changes in solvent-accessible surface area were calculated from available 3D structures, yielding a DeltaC(p) of -1.3 kJ mol(-1) K(-1); i.e., the experimentally determined heat capacity exceeds the calculated one. This implies that other thermodynamic factors exert a large influence on the heat capacity of protein-ligand interactions.
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Affiliation(s)
- A K Samland
- Institut für Pflanzenwissenschaften, Eidgenössische Technische Hochschule Zürich, Universitätstrasse 2, CH-8092 Zürich, Switzerland
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