Heat-Shock Response of the Haloalkaliphilic Archaeon Natronobacterium magadii

Ya. Yu. Polosina,¹ A. S. Kostyukova,^1,2 and O. V. Fedorov¹

¹Institute of Protein Research, Russian Academy of Science, Pushchino, Moscow Region, 142292 Russia; fax: (7-095) 924-04-93; E-mail: supra@vax.ipr.serpukhov.su

²To whom correspondence should be addressed.

Submitted April 4, 1996; revision submitted June 25, 1996.

Heat-shock response was studied at increased growth temperature (50, 55 and 60°C) for the haloalkaliphilic archaeon Natronobacterium magadii. Protein synthesis was monitored by [³⁵S]methionine incorporation into proteins at the various temperatures. The rate of synthesis of most cellular proteins at 50°C was slightly decreased, while the synthesis of a protein group with molecular masses ranging from 95 to 105 kD was increased. Protein synthesis at 55°C was repressed, and only six proteins with a molecular masses of about 40, 50, 65, 70, 105, and 140 kD continued to be synthesized. The synthesis of the 105 kD protein (Hsp105) at this temperature was 10 times higher than at 37°C. Only Hsp105 synthesis was still found at 60°C; this may be due to complete cell lysis at 60°C. It was also shown that Hsp105 is a cytosolic protein which does not form large multi-protein complexes like chaperonins. Also no ATPase activity for Hsp105 was found.

KEY WORDS: archaea, heat-shock proteins, Natronobacterium magadii.

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