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Conformations of arginine and lysine side chains in association with anions.

Authors
  • Chakrabarti, P
Type
Published Article
Journal
International journal of peptide & protein research
Publisher
Wiley (Blackwell Publishing)
Publication Date
Mar 01, 1994
Volume
43
Issue
3
Pages
284–291
Identifiers
PMID: 8005751
Source
Medline
License
Unknown

Abstract

The side chain conformations shown by arginine and lysine in amino-acid and peptide crystal structures and bound to oxyanions in proteins have been analyzed in an attempt to understand the behaviour of these long-chain amino acids in an ionic environment. Except for chi 1, torsions have a preference for the trans conformation. However, for arginine in protein structures, chi 3 and chi 4 appear to be flexible and can be tuned for optimal anion binding. For chi 4, values in the range -80 to 80 degrees are excluded for steric reasons; the remaining region in conformational space is accessible. This orientational variety exhibited by chi 4 has not been hitherto appreciated. Factors that can forbid a chi-angle to be in the trans geometry are the simultaneous binding of the anion by the main- and side-chain atoms, or the sharing of the anion between two different molecules in the crystal structure. Small molecules containing arginine have a distinct tendency to crystallize with two molecules in the asymmetric unit. This may be a general phenomenon for all extended molecules which have hydrogen-bond donors (or acceptors) embedded in a rigid set-up.

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