Conformational change and activation of cytochrome P450 2B1 induced by salt and phospholipid.
A stimulatory effect of increased salt concentration on the enzymatic activity of rat liver microsomes and a reconstituted system containing cytochrome P450 (P450) 2B1 and NADPH-P450 reductase was seen. Structural change of P450 2B1 accompanying the salt-induced increase in its enzyme activity was investigated by circular dichroism, fluorescence spectroscopy, and absorption spectroscopy. It was found that the salt increased alpha-helix content of P450 2B1 in the presence as well as in the absence of a phospholipid. Intrinsic fluorescence emissions also increased with increasing salt concentration. The low-spin iron configuration of P450 2B1 shifted toward the high-spin configuration in response to the increased salt concentration. It was found that the activity increase of P450 coincides with the raised alpha-helix content. The presence of phospholipid magnified this effect. It is proposed that the interaction with salts and phospholipid molecules surrounding P450 2B1 in the endoplasmic reticulum is important for a functional conformation of P450 2B1 in a monooxygenase system including NADPH-P450 reductase.
Department of Biochemistry, Pai-Chai University, Taejon, 302-735, Korea. chyun@woonam.paichai.ac.kr
C H
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Yun
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Ahn
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Guengerich
D000818:Animals; D002384:Catalysis / Q000187:drug effects; D002942:Circular Dichroism; D019362:Cytochrome P-450 CYP2B1 / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D008862:Microsomes, Liver / Q000201:enzymology; D010713:Phosphatidylcholines / Q000494:pharmacology; D010743:Phospholipids / Q000494:pharmacology*; D011487:Protein Conformation / Q000187:drug effects*; D051381:Rats; D012965:Sodium Chloride / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship
D010713:Phosphatidylcholines; D010743:Phospholipids; D012965:Sodium Chloride; D019362:Cytochrome P-450 CYP2B1