Nitric oxide binding to prokaryotic homologs of the soluble guanylate cyclase beta1 H-NOX domain.
The heme cofactor in soluble guanylate cyclase (sGC) is a selective receptor for NO, an important signaling molecule in eukaryotes. The sGC heme domain has been localized to the N-terminal 194 amino acids of the beta1 subunit of sGC and is a member of a family of conserved hemoproteins, called the H-NOX family (Heme-Nitric Oxide and/or OXygen-binding domain). Three new members of this family have now been cloned and characterized, two proteins from Legionella pneumophila (L1 H-NOX and L2 H-NOX) and one from Nostoc punctiforme (Np H-NOX). Like sGC, L1 H-NOX forms a 5-coordinate Fe(II)-NO complex. However, both L2 H-NOX and Np H-NOX form temperature-dependent mixtures of 5- and 6-coordinate Fe(II)-NO complexes; at low temperature, they are primarily 6-coordinate, and at high temperature, the equilibrium is shifted toward a 5-coordinate geometry. This equilibrium is fully reversible with temperature in the absence of free NO. This process is analyzed in terms of a thermally labile proximal Fe(II)-His bond and suggests that in both the 5- and 6-coordinate Fe(II)-NO complexes of L2 H-NOX and Np H-NOX, NO is bound in the distal heme pocket of the H-NOX fold. NO dissociation kinetics for L1 H-NOX and L2 H-NOX have been determined and support a model in which NO dissociates from the distal side of the heme in both 5- and 6-coordinate complexes.
Boon
Elizabeth M
EM
Department of Chemistry, University of California, Berkeley, California 94720.
Davis
Joseph H
JH
Department of Chemistry, University of California, Berkeley, California 94720.
Tran
Rosalie
R
Department of Chemistry, University of California, Berkeley, California 94720.
Karow
David S
DS
Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan 48109.
Huang
Shirley H
SH
Department of Molecular and Cell Biology, University of California, Berkeley, California 94720.
Pan
Duohai
D
Department of Chemistry, University of California, Berkeley, California 94720.
Miazgowicz
Michael M
MM
Department of Chemistry, University of California, Berkeley, California 94720.
Mathies
Richard A
RA
Department of Chemistry, University of California, Berkeley, California 94720; Division of Physical Biosciences, Lawrence Berkeley National Laboratory, Berkeley, California 94720.
Marletta
Michael A
MA
Department of Chemistry, University of California, Berkeley, California 94720; Department of Molecular and Cell Biology, University of California, Berkeley, California 94720; Division of Physical Biosciences, Lawrence Berkeley National Laboratory, Berkeley, California 94720. Electronic address: marletta@berkeley.edu.
D001665:Binding Sites; D006162:Guanylate Cyclase / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D007700:Kinetics; D016952:Legionella pneumophila / Q000201:enzymology; D009569:Nitric Oxide / Q000378:metabolism*; D046937:Nostoc / Q000201:enzymology; D012995:Solubility; D013696:Temperature
D009569:Nitric Oxide; D006418:Heme; D006162:Guanylate Cyclase