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The role of backbone stability near Ala 44 in the high reduction potential class of rubredoxins
Author(s) -
Tan MingLiang,
Kang ChulHee,
Ichiye Toshiko
Publication year - 2005
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.20806
Subject(s) - pyrococcus furiosus , rubredoxin , chemistry , crystallography , mutant , molecular dynamics , wild type , side chain , stereochemistry , biochemistry , computational chemistry , organic chemistry , archaea , gene , polymer
Rubredoxins may be separated into high and low reduction potential classes, with reduction potentials differing by ∼50 mV. Our previous work showed that a local shift in the polar backbone due to an A 44 versus V 44 side‐chain size causes this reduction potential difference. However, this work also indicated that in the low potential Clostridium pasteurianum (Cp) rubredoxin, a V 44 → A 44 mutation causes larger local backbone flexibility, because the V 44 side‐chain present in the wild‐type (wt) is no longer present to interlock with neighboring residues to stabilize the subsequent G 45 . Since Pyrococcus furiosus (Pf) and other high potential rubredoxins generally have a P 45 , it was presumed that a G 45 → P 45 mutation might stabilize a V 44 → A 44 mutation in Cp rubredoxin. Here crystal structure analysis, energy minimization, and molecular dynamics (MD) were performed for wt V 44 G 45 , single mutant A 44 G 45 and double mutant A 44 P 45 Cp, and for wt A 44 P 45 Pf rubredoxins. The local structural, dynamical, and electrostatic properties of Cp gradually approach wt Pf in the order wt Cp to single to double mutant because of greater sequence similarity, as expected. The double mutant A 44 P 45 Cp exhibits increased backbone stability near residue 44 and thus enhances the probability that the backbone dipoles point toward the redox site, which favors an increase in the electrostatic contribution to the reduction potential. It appears that the electrostatic potential of residue 44 and the solvent accessibility to the redox are both determinants for the reduction potentials of homologous rubredoxins. Overall, these results indicate that an A 44 in a rubredoxin may require a P 45 for backbone stability whereas a V 44 can accommodate a G 45 , since the valine side‐chain can interlock with its neighbors. Proteins 2006. © 2005 Wiley‐Liss, Inc.