title: The truncated hemoglobin from Mycobacterium leprae.
abstract: Truncated hemoglobins (trHb's) form a family of low molecular weight O2 binding hemoproteins distributed in eubacteria, protozoa, and plants. TrHb's branch in a distinct clade within the hemoglobin (Hb) superfamily. A unique globin gene has recently been identified from the complete genome sequence of Mycobacterium leprae that is predicted to encode a trHb (M. leprae trHbO). Sequence comparison and modelling considerations indicate that monomeric M. leprae trHbO has structural features typical of trHb's, such as 20-40 fewer residues than conventional globin chains, Gly-based sequence consensus motifs, likely assembling into a 2-on-2 alpha-helical sandwich fold, and hydrophobic residues recognized to build up the protein matrix ligand diffusion tunnel. The ferrous heme iron atom of deoxygenated M. leprae trHbO appears to be hexacoordinated, like in Arabidopsis thaliana trHbO-3 (A. thaliana trHbO-3). Accordingly, the value of the second-order rate constant for M. leprae trHbO carbonylation (7.3 x 10(3) M(-1) s(-1)) is similar to that observed for A. thaliana trHbO-3 (1.4 x 10(4) M(-1) s(-1)) and turns out to be lower than that reported for carbon monoxide binding to pentacoordinated Mycobacterium tuberculosis trHbN (6.7 x 10(6) M(-1) s(-1)). The lower reactivity of M. leprae trHbO as compared to M. tuberculosis trHbN might be related to the higher susceptibility of the leprosy bacillus to toxic nitrogen and oxygen species produced by phagocytic cells.
authors.affiliation: Dipartimento di Biologia e Laboratorio Interdipartimentale di Microscopia Elettronica, Università Roma Tre, Viale G. Marconi 446, I-00146 Rome, Italy. visca@bio.uniroma3.it
authors.forename: Paolo
authors.initials: P
authors.lastname: Visca
authors.forename: Giulia
authors.initials: G
authors.lastname: Fabozzi
authors.forename: Andrea
authors.initials: A
authors.lastname: Petrucca
authors.forename: Chiara
authors.initials: C
authors.lastname: Ciaccio
authors.forename: Massimo
authors.initials: M
authors.lastname: Coletta
authors.forename: Giampiero
authors.initials: G
authors.lastname: De Sanctis
authors.forename: Martino
authors.initials: M
authors.lastname: Bolognesi
authors.forename: Mario
authors.initials: M
authors.lastname: Milani
authors.forename: Paolo
authors.initials: P
authors.lastname: Ascenzi
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D003001:Cloning, Molecular; D006454:Hemoglobins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009166:Mycobacterium leprae; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013053:Spectrophotometry; D054793:Truncated Hemoglobins
chemical_list: D001426:Bacterial Proteins; D006454:Hemoglobins; D008024:Ligands; D011994:Recombinant Proteins; D054793:Truncated Hemoglobins; C460871:truncated hemoglobin, Mycobacterium leprae