Active Site Structures of CYP11A1 in the Presence of Its Physiological Substrates and Alterations upon Binding of Adrenodoxin.
Active Site Structures of CYP11A1 in the Presence of Its Physiological Substrates and Alterations upon Binding of Adrenodoxin.
复制标题
CYP11A1 在其生理底物存在下的活性位点结构以及与肾上腺素结合后的变化。
DOI：
10.1021/acs.biochem.7b00766
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发表时间：
2017
期刊：
影响因子：
2.9
通讯作者：
Kincaid,JamesR
中科院分区：
文献类型：
--
作者：
Zhu,Qianhong;Mak,PiotrJ;Tuckey,RobertC;Kincaid,JamesR
The rate-limiting step in the steroid synthesis pathway is catalyzed by CYP11A1 through three sequential reactions. The first two steps involve hydroxylations at positions 22 and 20, generating 20(R),22(R)-dihydroxycholesterol (20R,22R-DiOHCH), with the third stage leading to a C20–C22 bond cleavage, forming pregnenolone. This work provides detailed information about the active site structure of CYP11A1 in the resting state and substrate-bound ferric forms as well as the CO-ligated adducts. In addition, high-quality resonance Raman spectra are reported for the dioxygen complexes, providing new insight into the status of Fe–O–O fragments encountered during the enzymatic cycle. Results show that the three natural substrates of CYP11A1 have quite different effects on the active site structure, including variations of spin state populations, reorientations of heme peripheral groups, and, most importantly, substrate-mediated distortions of Fe–CO and Fe–O2fragments, as revealed by telltale shifts of the observed vibrational modes. Specifically, the vibrational mode patterns observed for the Fe–O–O fragments with the first and third substrates are consistent with H-bonding interactions with the terminal oxygen, a structural feature that tends to promote O–O bond cleavage to form the Compound I intermediate. Furthermore, such spectral data are acquired for complexes with the natural redox partner, adrenodoxin (Adx), revealing protein–protein-induced active site structural perturbations. While this work shows that Adx has an only weak effect on ferric and ferrous CO states, it has a relatively stronger impact on the Fe–O–O fragments of the functionally relevant oxy complexes.
