title: Ligand- and proton-linked conformational changes of the ferrous 2/2 hemoglobin of Pseudoalteromonas haloplanktis TAC125.
abstract: The spectroscopic and ligand-binding properties of a 2/2 globin from the Antarctic bacterium Pseudoalteromonas haloplanktis TAC125 have been studied in the ferrous state. It displays two major conformations characterized by CO-association rates that differ by a factor of 20, with relative fractions that depend on pH. A dynamic equilibrium is found between the two conformations, as indicated by an enhanced slower phase when lower CO levels were used to allow a longer time to facilitate the transition. The deoxy form, in the absence of external ligands, is a mixture of a predominant six-coordinate low spin form and a five-coordinate high-spin state; the proportion of low spin increasing at alkaline pH. In addition, at temperatures above the physiological temperature of 1 °C, an enhanced tendency of the protein to oxidize is observed.
authors.affiliation: Institute of Protein Biochemistry, CNR, Naples, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Giordano
authors.forename: Roberta
authors.initials: R
authors.lastname: Russo
authors.forename: Chiara
authors.initials: C
authors.lastname: Ciaccio
authors.forename: Barry D
authors.initials: BD
authors.lastname: Howes
authors.forename: Guido
authors.initials: G
authors.lastname: di Prisco
authors.forename: Michael C
authors.initials: MC
authors.lastname: Marden
authors.forename: Gaston
authors.initials: G
authors.lastname: Hui Bon Hoa
authors.forename: Giulietta
authors.initials: G
authors.lastname: Smulevich
authors.forename: Massimo
authors.initials: M
authors.lastname: Coletta
authors.forename: Cinzia
authors.initials: C
authors.lastname: Verde
mesh_terms: D000864:Antarctic Regions; D002248:Carbon Monoxide / Q000378:metabolism; D006454:Hemoglobins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008024:Ligands; D011487:Protein Conformation; D011522:Protons; D031161:Pseudoalteromonas / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature
chemical_list: D006454:Hemoglobins; D008024:Ligands; D011522:Protons; D002248:Carbon Monoxide