Resonance Raman evidence for the presence of two heme pocket conformations with varied activities in CO-bound bovine soluble guanylate cyclase and their conversion.
Resonance Raman (RR) spectra of soluble guanylate cyclase (sGC) reported by five independent research groups have been classified as two types: sGC(1) and sGC(2). Here we demonstrate that the RR spectra of sGC isolated from bovine lung contain only sGC(2) while both species are observed in the spectra of the CO-bound form (CO-sGC). The relative populations of the two forms were altered from an initial composition in which the CO-sGC(2) form predominated, with the Fe-CO (nu(Fe)(-)(CO)) and C-O stretching modes (nu(CO)) at 472 and 1985 cm(-)(1), respectively, to a composition dominated by the CO-sGC(1) form with nu(Fe)(-)(CO) and nu(CO) at 488 and 1969 cm(-)(1), respectively, following the addition of a xenobiotic, YC-1. Further addition of a substrate, GTP, completed the change. GDP and cGMP had a significantly weaker effect, while a substrate analogue, GTP-gamma-S, had an effect similar to that of GTP. In contrast, ATP had a reverse effect, and suppressed the effects of YC-1 and GTP. In the presence of both YC-1 and GTP, vinyl vibrations of heme were significantly influenced. New CO isotope-sensitive bands were observed at 521, 488, 363, and 227 cm(-)(1). The 521 cm(-)(1) band was assigned to the five-coordinate (5c) species from the model compound studies using ferrous iron protoporphyrin IX in CTAB micelles. Distinct from the 472 cm(-)(1) species, both the 488 and 521 cm(-)(1) species were apparently un-photodissociable when an ordinary Raman spinning cell was used, indicating rapid recombination of photodissociated CO. On the basis of these findings, binding of YC-1 to the heme pocket is proposed.
Li
Zhengqiang
Z
Okazaki Institute for Integrative Bioscience, National Institute of Natural Sciences, Myodaiji, Okazaki 444-8787, Japan.
Pal
Biswajit
B
Takenaka
Shigeo
S
Tsuyama
Shingo
S
Kitagawa
Teizo
T
D000494:Allosteric Regulation; D000818:Animals; D002248:Carbon Monoxide / Q000378:metabolism*; D002417:Cattle; D006150:Guanine Nucleotides / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D011485:Protein Binding; D013059:Spectrum Analysis, Raman
D006150:Guanine Nucleotides; D006418:Heme; D002248:Carbon Monoxide; D006162:Guanylate Cyclase