title: Mutational study of the bacterial hemoglobin distal heme pocket.
abstract: Ligand binding experiments on three mutants in the distal heme pocket of Vitreoscilla hemoglobin (GlnE7His, ProE8Ala, and GlnE7His,ProE8Ala) were used to probe the role of GlnE7 and ProE8 in the pocket's unusual structure. The oxygen dissociation constants for the wild type, E8Ala mutant, and E7His mutant proteins were 4.5, 4.7, and 1.7microM, respectively; the K(d) for the double mutant was not determinable by our technique. Visible-Soret spectra of the carbonyl and cyanyl forms and FT-IR of the carbonyl form of the E8 mutant were similar to those of the wild type; the opposite was true for the GlnE7His and GlnE7His,ProE8Ala mutants, which also differed from wild type in the visible-Soret spectra of their oxidized forms. Models of the effects of the mutations on distal pocket structure were consistent with the experimental findings, particularly the larger effects of the GlnE7His change.
authors.affiliation: Biology Division, Department of Biological, Chemical, and Physical Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA.
authors.forename: Sandhya
authors.initials: S
authors.lastname: Verma
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Patel
authors.forename: Ramandeep
authors.initials: R
authors.lastname: Kaur
authors.forename: Yeon-Tae
authors.initials: YT
authors.lastname: Chung
authors.forename: Brian T
authors.initials: BT
authors.lastname: Duk
authors.forename: Kanak L
authors.initials: KL
authors.lastname: Dikshit
authors.forename: Benjamin C
authors.initials: BC
authors.lastname: Stark
authors.forename: Dale A
authors.initials: DA
authors.lastname: Webster
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002248:Carbon Monoxide / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D006418:Heme / Q000378:metabolism*; D006454:Hemoglobins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics*; D010100:Oxygen / Q000378:metabolism; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared; D054793:Truncated Hemoglobins; D020589:Vitreoscilla / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D006454:Hemoglobins; D054793:Truncated Hemoglobins; C082613:hemoglobin protein, Vitreoscilla; D006418:Heme; D002248:Carbon Monoxide; D010100:Oxygen