CO binding study of mouse heme-regulated eIF-2alpha kinase: kinetics and resonance Raman spectra.
Heme-regulated eukaryotic initiation factor (eIF)-2alpha kinase (HRI) regulates the synthesis of globin chains in reticulocytes with heme availability. In the present study, CO binding kinetics to the 6-coordinated Fe(II) heme of the amino-terminal domain of mouse HRI and resonance Raman spectra of the Fe(II)-CO complex are examined to probe the character of the heme environment. The CO association rate constant, k(on)', and CO dissociation rate constant, k(off), were 0.0029 microM(-1)s(-1) and 0.003 s(-1), respectively. These values are very slow compared with those of mouse neuroglobin and sperm whale myoglobin, while the k(off) value of HRI was close to those of the 6-coordinated hemoglobins from Chlamydomonas and barley (0.0022 and 0.0011 s(-1)). The dissociation rate constant of an endogenous ligand, which occurs prior to CO association, was 18.3 s(-1), which was lower than those (197 and 47 s(-1)) of the same 6-coordinated hemoglobins. Resonance Raman spectra suggest that the Fe-C-O adopts an almost linear and upright structure and that the bound CO interacts only weakly with nearby amino acid residues.
Igarashi
Jotaro
J
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
Sato
Akira
A
Kitagawa
Teizo
T
Sagami
Ikuko
I
Shimizu
Toru
T
D000818:Animals; D002248:Carbon Monoxide / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D013053:Spectrophotometry; D013059:Spectrum Analysis, Raman; D019892:eIF-2 Kinase / Q000302:isolation & purification / Q000378:metabolism*
D006418:Heme; D002248:Carbon Monoxide; D019892:eIF-2 Kinase