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The crystal structure of the cis ‐proline to glycine variant (P114G) of ribonuclease A
Author(s) -
Schultz David A.,
Friedman Alan M.,
White Mark A.,
Fox Robert O.
Publication year - 2005
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.051610505
Subject(s) - chemistry , peptide bond , ribonuclease , peptide , crystallography , residue (chemistry) , isomerization , stereochemistry , proline , thermal stability , protein folding , glycine , kinetics , protein structure , amino acid , biochemistry , catalysis , rna , gene , physics , organic chemistry , quantum mechanics
Replacement of a cis ‐proline by glycine at position 114 in ribonuclease A leads to a large decrease in thermal stability and simplifies the refolding kinetics. A crystallographic approach was used to determine whether the decrease in thermal stability results from the presence of a cis glycine peptide bond, or from a localized structural rearrangement caused by the isomerization of the mutated cis 114 peptide bond. The structure was solved at 2.0 Å resolution and refined to an R‐factor of 19.5% and an R free of 21.9%. The overall conformation of the protein was similar to that of wild‐type ribonuclease A; however, there was a large localized rearrangement of the mutated loop (residues 110–117—a 9.3 Å shift of the Cα atom of residue 114). The peptide bond before Gly114 is in the trans configuration. Interestingly, a large anomalous difference density was found near residue 114, and was attributed to a bound cesium ion present in the crystallization experiment. The trans isomeric configuration of the peptide bond in the folded state of this mutant is consistent with the refolding kinetics previously reported, and the associated protein conformational change provides an explanation for the decreased thermal stability.