pKa calculations for class C β-lactamases: The role of tyr-150
The Poisson‐Boltzmann method was used to compute the pKa values of titratable residues in a set of class C β‐lactamases. In these calculations, the pKa of the phenolic group of residue Tyr150 is the only one to stand out with an abnormally low value of 8.3, more than one pKa unit lower than the meas...
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Published in | Proteins, structure, function, and bioinformatics Vol. 40; no. 1; pp. 23 - 28 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
New York
John Wiley & Sons, Inc
01.07.2000
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Subjects | |
Online Access | Get full text |
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Summary: | The Poisson‐Boltzmann method was used to compute the pKa values of titratable residues in a set of class C β‐lactamases. In these calculations, the pKa of the phenolic group of residue Tyr150 is the only one to stand out with an abnormally low value of 8.3, more than one pKa unit lower than the measured reference value for tyrosine in solution. Other important residues of the catalytic pocket, such as the conserved Lys67, Lys315, His314, and Glu272 (hydrogen‐bonded to the ammonium group of Lys315), display normal protonation states at neutral pH. pKa values were also computed in catalytically impaired β‐lactamase mutants. Comparisons between the relative kcat values and the Tyr150 pKa value in these mutants revealed a striking correlation. In active enzymes, this pKa value is always lower than the solution reference value while it is close to normal in inactive enzymes. These results thus support the hypothesis that the phenolate form of Tyr150 is responsible for the activation of the nucleophilic serine. The possible roles of Lys67 and Lys315 during catalysis are also discussed. Proteins 2000;40:23–28. © 2000 Wiley‐Liss, Inc. |
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Bibliography: | Belgian Government Pôle d'attraction Interuniversitaire - No. P4/03 Loterie Nationale (Belgian Fonds de la Recherche Scientifique) - No. 9.4585.92 ArticleID:PROT40 istex:EE5BCAC1DDEC931C0D4079C093D60B61FDE027A8 ark:/67375/WNG-PPJ4ZMJV-L |
ISSN: | 0887-3585 1097-0134 |
DOI: | 10.1002/(SICI)1097-0134(20000701)40:1<23::AID-PROT40>3.0.CO;2-7 |