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Functional implications of the proximal site hydrogen bonding network in Vitreoscilla hemoglobin (VHb): Role of Tyr95 (G5) and Tyr126 (H12)
Author(s) -
Kaur Ramandeep,
Ahuja Sandhya,
Anand Arvind,
Singh Balwinder,
Stark Benjamin. C.,
Webster Dale. A.,
Dikshit Kanak L.
Publication year - 2008
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2008.09.018
Subject(s) - mutant , chemistry , hydrogen bond , hemoglobin , oxygen , nitric oxide , biochemistry , molecule , gene , organic chemistry
Although Vitreoscilla hemoglobin (VHb) carries a conventional globin fold, its proximal site geometry is unique in having a hydrogen‐bonding network between proximal site residues, HisF8‐TyrG5‐GluH23 and TyrG5‐TyrH12. TyrG5 and TyrH12 were mutated to study their relevance in VHb function. VHb G5 mutants (Tyr95Phe and Tyr95Leu showed no stable oxyform and nitric oxide dioxygenase activity, whereas, VHb H12 mutants (Tyr126Phe and Tyr126Leu) displayed little change in their oxygen affinity indicating a crucial role of Tyr95 in protein function. The VHb H12 mutant, Tyr126Leu, enhanced the intracellular pool of oxygen and cell growth better than VHb. Molecular modeling suggests that the replacement of tyrosine with leucine in Tyr126Leu creates an opening on the protein surface that may facilitate oxygen diffusion and accumulation.