STRUCTURAL BASES FOR SULFIDE RECOGNITION IN LUCINA-PECTINATA HEMOGLOBIN-I

Citation
M. Rizzi et al., STRUCTURAL BASES FOR SULFIDE RECOGNITION IN LUCINA-PECTINATA HEMOGLOBIN-I, Journal of Molecular Biology, 258(1), 1996, pp. 1-5
Citations number
28
Categorie Soggetti
Biology
ISSN journal
00222836
Volume
258
Issue
1
Year of publication
1996
Pages
1 - 5
Database
ISI
SICI code
0022-2836(1996)258:1<1:SBFSRI>2.0.ZU;2-W
Abstract
The X-ray crystal structure of the sulfide derivative of ferric Lucina pectinata hemoglobin component I (HbI) has been determined at 1.9 Ang strom resolution (R-factor 0.186). The heme pocket structural organiza tion of HbI is in keeping with its ligand binding properties. The fast sulfide association rate constant can be related to the presence of G ln(64)E7, as the heme distal residue, together with the protein struct ural properties in the CD-E distal region. Moreover, the very high sul fide affinity for HbI is reflected by the exceptionally slow ligand di ssociation rate. The stabilization of the heme-bound sulfide molecule is achieved through hydrogen bonding to Gln(64)E7, as well as by finel y tuned aromatic-electrostatic interactions with the clustered residue s Phe(29)B10, Phe(43)CD1 and Phe(68)E11. Such a peculiar arrangement o f phenylalanyl residues at the distal ligand binding site has not been observed before in the globin family, and is unique to HbI, a protein functionally devoted to sulfide transport. (C) 1996 Academic Press Li mited