Suzanne Zoë Fisher, Heiner N Raum, Ulrich Weininger
{"title":"Proton Occupancies in Histidine Side Chains of Carbonic Anhydrase II by Neutron Crystallography and NMR - Differences, Similarities and Opportunities.","authors":"Suzanne Zoë Fisher, Heiner N Raum, Ulrich Weininger","doi":"10.1002/cbic.202400930","DOIUrl":null,"url":null,"abstract":"<p><p>Histidine is a key amino-acid residues in proteins that can exist in three different protonation states: two different neutral tautomeric forms and a protonated, positively charged one. It can act as both donor and acceptor of hydrogen bonds, coordinate metal ions, and engage in acid/base catalysis. Human Carbonic Anhydrase II (HCA II) is a pivotal enzyme catalyzing the reversible hydration of carbon dioxide. It contains 12 histidine residues: six surface exposed, two buried, three active site zinc ion ligands, and one is a proton shuttle. Comparing results from NMR spectroscopy with previously determined neutron protein crystal structures enabled a side-by-side investigation of the proton occupancies and preferred tautomeric states of the histidine residues in HCA II. Buried and zinc coordinating histidines remain in one neutral tautomeric state across the entire pH range studied, as validated by both methods. In contrast, solvent-exposed histidines display high variability in proton occupancies. While the data were overall remarkably consistent between methods, some discrepancies were observed, shedding light on the limitations of each technique. Therefore, combining these methods with full awareness of the advantages and drawbacks of each, provides insights into the dynamic protonation landscape of HCA II histidines, crucial for elucidating enzyme catalytic mechanisms.</p>","PeriodicalId":140,"journal":{"name":"ChemBioChem","volume":" ","pages":"e202400930"},"PeriodicalIF":2.6000,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"ChemBioChem","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1002/cbic.202400930","RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"BIOCHEMISTRY & MOLECULAR BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Histidine is a key amino-acid residues in proteins that can exist in three different protonation states: two different neutral tautomeric forms and a protonated, positively charged one. It can act as both donor and acceptor of hydrogen bonds, coordinate metal ions, and engage in acid/base catalysis. Human Carbonic Anhydrase II (HCA II) is a pivotal enzyme catalyzing the reversible hydration of carbon dioxide. It contains 12 histidine residues: six surface exposed, two buried, three active site zinc ion ligands, and one is a proton shuttle. Comparing results from NMR spectroscopy with previously determined neutron protein crystal structures enabled a side-by-side investigation of the proton occupancies and preferred tautomeric states of the histidine residues in HCA II. Buried and zinc coordinating histidines remain in one neutral tautomeric state across the entire pH range studied, as validated by both methods. In contrast, solvent-exposed histidines display high variability in proton occupancies. While the data were overall remarkably consistent between methods, some discrepancies were observed, shedding light on the limitations of each technique. Therefore, combining these methods with full awareness of the advantages and drawbacks of each, provides insights into the dynamic protonation landscape of HCA II histidines, crucial for elucidating enzyme catalytic mechanisms.
期刊介绍:
ChemBioChem (Impact Factor 2018: 2.641) publishes important breakthroughs across all areas at the interface of chemistry and biology, including the fields of chemical biology, bioorganic chemistry, bioinorganic chemistry, synthetic biology, biocatalysis, bionanotechnology, and biomaterials. It is published on behalf of Chemistry Europe, an association of 16 European chemical societies, and supported by the Asian Chemical Editorial Society (ACES).