TAILIEUCHUNG - Báo cáo Y học: Escherichia coli small heat shock proteins, IbpA and IbpB, protect enzymes from inactivation by heat and oxidants

To examine functions of two small heat shock proteins of Escherichia coli, IbpA and IbpB, we constructed His–IbpA and His–IbpB, in which a polyhistidine tag was fused to the N-terminals. Both purified His–IbpA and His–IbpB formed multimers, which have molecular masses of about – MDa and consist of about 100–150 subunits. They suppressed the inactivation of several enzymes including citrate synthase and 6-phosphogluconate dehydrogenase by heat, potassium superoxide, hydrogen peroxide and freezethawing, but not the inactivation of glyceraldehyde-3phosphate dehydrogenase by hydrogen peroxide | Eur. J. Biochem. 269 2907-2917 2002 FEBS 2002 doi Escherichia colismall heat shock proteins IbpA and IbpB protect enzymes from inactivation by heat and oxidants Masanobu Kitagawa Mizuho Miyakawa Yoshinobu Matsumura and Tetsuaki Tsuchido Department of Biotechnology Faculty of Engineering Kansai University Suita Osaka Japan To examine functions of two small heat shock proteins of Escherichia coli IbpA and IbpB we constructed His-IbpA and His-IbpB in which a polyhistidine tag was fused to the N-terminals. Both purihed Hss-IbpA and His IbpB formed multimers which have molecular masses of about MDa and consist of about 100-150 subunits. They suppressed the inactivation of several enzymes including citrate synthase and 6-phosphogluconate dehydrogenase by heat potassium superoxide hydrogen peroxide and freezethawing but not the inactivation of glyceraldehyde-3-phosphate dehydrogenase by hydrogen peroxide. Both His-IbpA and His-IbpB suppressed enzyme inactivation by various treatments and were also found to be associated with their non-native forms. However both Hís-IbpA and HỈ--IbpB were not able to reactivate enzymes inactivated by heat oxidants or guanidine hydrochloride. When heaied to 50 C each multimeric form of His-IbpA or His-IbpB was dissociated to form a monomer for His-IbpA and an oligomer of about one-quarter size for His-IbpB. Thcee tlruc-tural changes were reversible as both heated proteins regained the multimeric structures after incubation at 25 C. However when exposed to hydrogen peroxide or potassium superoxide the large multimeric forms of His-IbpA and His-IbpB were maintained. Tire esuld te rughPSt dial Hì-IbpA and His-IbpB suppress the inactivation of enzymes and bind non-native proteins to protect their structures from heat and oxidants. Keywords small HSP heat shock oxidants enzyme inactivation multimeric structure. In response to heat cells increase the expression of heat shock proteins HSPs to protect .

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