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Professor Hitoshi Nakamoto
Department of Biochemistry and Molecular Biology, Saitama University, Japan
Title of the talk: Multiple ClpBs and GroELs/chaperonins in cyanobacteria: novel chaperones for basic and applied research
Molecular chaperones are involved in protein homeostasis. Stress disturbs protein homeostasis in a cell. Elevated expression of molecular chaperone(s) increases cellular tolerances against high/low temperature stress, high-salt stress, oxidative stress, acid stress, and other stresses. Cellular tolerance to toxic metabolites is an important property of a strain for many biotechnological applications such as the production of biofuels. Expression/tuned co-overexpression of molecular chaperone(s) improves tolerance against solvents such as ethanol and butanol. Thus expanding our knowledge of molecular chaperones will increase the potential for their biotechnological applications.
Cyanobacteria may be one of the most useful microorganisms to elucidate functions/roles of molecular chaperones under stress since cyanobacteria have encountered various environmental stresses during evolution and it is conceivable that molecular chaperones have been deeply involved in the adaptations to environmental stresses.
In contrast to E. coli, cyanobacteria have multiple clpB, and groEL genes. ClpB and GroEL (Chaperonin) are the evolutionarily conserved molecular chaperones which play vital roles under stress. The homologous genes in each chaperone family appear to be regulated differentially, and have different physiological properties. For example, the cyanobacterium Synechococcus elongatus has two GroELs (GroEL1 and GroEL2). GroEL1 is essential like the E. coli GroEL, while GroEL2 is not essential. It has two ClpBs (ClpB1 and ClpB2). ClpB1 is not essential and induced under stress like the E.coli ClpB, while ClpB2 is constitutively expressed and an essential protein. We have been working on the cyanobacterial molecular chaperones in order to discover novel chaperone functions/mechanisms. I will present our results obtained by comparative biochemical studies on GroEL and ClpB homologs in cyanobacteria. Our data showed a great biochemical diversity among the homologs. The diversity may play an important role in the face of multiple stressors and open up further possibilities for biotechnological applications of molecular chaperones.
Hitoshi Nakamoto has completed his PhD from Washington State University in USA and continued postdoctoral studies at University of Sheffield in UK, Umeå University in Sweden, and Washington State University. After working at the University of Tokyo as an assistant professor, he is now an associate professor at Saitama University. He has been a visiting researcher/professor at the Roche Institute of Molecular Biology, University of Michigan, and Universiti Kebangsaan Malaysia. He has published about 80 papers in international journals.