The occupancy of two distinct conformations by active‐site histidine‐119 in crystals of ribonuclease is modulated by pH

FEBS Letters

Doscher, Marilynn S.¹  Edwards, Brian F.P.¹  J. de Mel, V.Srini¹  Martin, Philip D.¹ 

[1] Department of Biochemistry, Wayne State University School of Medicine, 540 East Canfield Ave. Detroit, MI 48201, USA

关键词: Mobile histidine;    Modulation of conformation by pH;    Protein semisynthesis;    RNase mechanism of action;    Semisynthetic RNase;    X-ray structure;    RNase A;    bovine pancreatic ribonuclease A;    RNase 1-118;    polypeptide consisting of residues 1 through 118 of RNase A;    RNase 111–124;    tetradecapeptide consisting of residues 111–124 of RNase A;    RNase 111–124[Tyr-120];    tetradecapeptide in which Phe-120 is replaced by Tyr;    RNase 1–118:111–124;    noncovalent complex of RNase 1–118 and RNase 111–124;    (F120Y);    noncovalent complex of RNase 1–118 and RNase 111–124[Tyr-120] in which Phe-120 is replaced by Tyr;    UpA;    uridylyl-3′;    5′-adenosine;    UpcA;    UpA in which the 5′ oxygen of the ribose moiety of the adenosine is replaced by a methylene group;   

DOI  :  10.1016/0014-5793(94)00664-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Structures of a semisynthetic RNase have been obtained to a resolution of 2.0 Å at pH values of 5.2, 6.5, 7.5, and 8.8, respectively. The principle structural transformation occurring over this pH range is the conversion of the side chain of active site residue His-119 from one conformation (X ₁ = −43° to −57°) at low pH to another (X ₁ = + 159° to + 168°) at higher pH values. On the basis of this observation, a model is proposed that reconciles the disparate pK values for His-119 in the enzyme-substrate complex that have been deduced from kinetic studies and from proton NMR measurements in the presence of pseudosubstrates.

【 授权许可】

Unknown