Characterization of an Escherichia coli Sulfite Oxidase Homologue Reveals the Role of a Conserved Active Site Cysteine in Assembly and Function

详细信息    查看全文

• 作者：Stephen J. Brokx ; Richard A. Rothery ; Guijin Zhang ; Derek P. Ng ; and Joel H. Weiner
• 刊名：Biochemistry
• 出版年：2005
• 出版时间：August 2, 2005
• 年：2005
• 卷：44
• 期：30
• 页码：10339 - 10348
• 全文大小：171K
• 年卷期：v.44,no.30(August 2, 2005)
• ISSN：1520-4995

文摘

We report the biochemical and biophysical characterization of YedYZ, a sulfite oxidasehomologue from Escherichia coli. YedY is a soluble catalytic subunit with a twin arginine leader sequencefor export to the periplasm by the Tat translocation system. YedY is the only molybdoenzyme so farisolated from E. coli with the Mo-MPT form of the molybdenum cofactor. The electron paramagneticresonance (EPR) signal of the YedY molybdenum is similar to that of known Mo-MPT containing enzymes,with the exception that only the Mo(IV) Mo(V) transition is observed, with a midpoint potential of132 mV. YedZ is a membrane-intrinsic cytochrome b with six putative transmembrane helices. The singleheme b of YedZ has a midpoint potential of -8 mV, determined by EPR spectroscopy of YedZ-enrichedmembrane preparations. YedY does not associate strongly with YedZ on the cytoplasmic membrane.However, mutation of the YedY active site Cys102 to Ser results in very efficient targeting of YedY toYedZ in the membrane, demonstrating a clear role for YedZ as the membrane anchor for YedY. Together,YedYZ comprise a well-conserved bacterial heme-molybdoenzyme found in a variety of bacteria that canbe assigned to the sulfite oxidase class of enzyme.