Page 12 - U. Protein structure and function

[U. Protein structure and function-8]

Polaribacter irgensii KOPRI 22228 cspB expression greatly

increases freeze-tolerance of the host

Youn Hong Jung¹, Hana Im¹

¹Integrative Bioscience and Biotechnology, Sejong University, Seoul 05006, Republic of Korea

Since psychrophilic organisms from cold ecosystems must have a mechanism to survive extremely cold temperatures,
the roles played by cold shock proteins (Csps) from polar bacteria have been studied to understand the mechanism
of cold adaptation. Overexpression of cspBPi from the Arctic bacterium Polaribacter irgensii KOPRI 22228 conferred

extraordinary freezing tolerance to its host. To elucidate the detailed mechanisms involved in the extraordinary

freeze-tolerance conferred by cspBPi, mutations in the well-conserved C-terminal cold shock domain (CSD), that
are crucial for binding RNA or single-stranded DNA, were introduced. These mutations did not hamper the ability
of the host to survive freezing stress. When the effects of domain-deletion and domain-shuffling of cspBPi were

analyzed, all cspBPi variants containing the unique N-terminal domain retained the ability to confer the prominent
cold-resistance. Far-UV circular dichroism spectra and slow electrophoretic mobility suggested that the N-terminal

domain is intrinsically disordered. The N-terminal domain bound to lipid vesicles in vitro, that is a characteristics
shared with other intrinsically disordered proteins known to confer cold-tolerance, suggesting a mechanism for

cold-tolerance through membrane binding.