Bulletin of the Chemical Society of Japan
Weak Nonbonded S···X (X = O, N, and S) Interactions in Proteins. Statistical and Theoretical Studies.
Michio IwaokaShinya TakemotoMai OkadaShuji Tomoda
Author information
JOURNALS RESTRICTED ACCESS

Volume 75 (2002) Issue 7 Pages 1611-1625

Details
View on the journal site Contact us
Abstract

Sulfur-containing functional groups of cystine (an SSC group) and methionine (a CSC group) are usually considered as hydrophobic moieties or weak hydrogen-bond acceptors in folded protein structures. However, database analysis as well as theoretical calculations carried out in this study have provided strong evidence for the presence of specific nonbonded interactions between the divalent sulfur atoms (S) and nearby polar non-hydrogen atoms (X). Close S···X (X = O, N, S, C, etc.) atomic contacts were statistically analyzed in 604 high-resolution heterogeneous X-ray structures selected from a protein databank (PDB_SELECT). The S···O interactions found for both SSC and CSC groups showed a specific character as a π(C=O) → σ*(S) orbital interaction based on the directional preferences. The interactions were most frequently observed in α-helices. Ab initio calculations applying the second order Møller–Plesset perturbation theory (MP2) suggested the primary importance of electron correlations. The total stabilization energies were calculated to be ∼3.2 and ∼2.5 kcal/mol for SSC and CSC groups, respectively, including the contribution from a coexisting CH···O hydrogen bond. On the other hand, the S···N interactions observed for a CSC group exhibited structural characters as a π(N) → σ*(S) orbital interaction and an NH···S hydrogen bond, and the S···S interactions for an SSC group showed a structural character as an n(S) → σ*(S) orbital interaction. The S···C(π) interactions should be rather weak and long-range.

Information related to the author
© 2002 The Chemical Society of Japan
Previous article Next article

Recently visited articles
feedback
Top