Functional implications of the proximal site hydrogen bonding network in Vitreoscilla hemoglobin (VHb): role of Tyr95 (G5) and Tyr126 (H12).
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.
Kaur
Ramandeep
R
Institute of Microbial Technology, Sector 39 A, Chandigarh 160036, India.
Ahuja
Sandhya
S
Anand
Arvind
A
Singh
Balwinder
B
Stark
Benjamin C
BC
Webster
Dale A
DA
Dikshit
Kanak L
KL
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D006860:Hydrogen Bonding; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D054793:Truncated Hemoglobins / Q000737:chemistry* / Q000235:genetics; D014443:Tyrosine / Q000737:chemistry* / Q000235:genetics
D001426:Bacterial Proteins; D008024:Ligands; D054793:Truncated Hemoglobins; C082613:hemoglobin protein, Vitreoscilla; D014443:Tyrosine