MOLECULAR CHARACTERIZATION OF GUANOSINE KINASE GENE FROM A FACULTATIVE ALKALOPHILE, EXIGUOBACTERIUM-AURANTIACUM ATCC-35652

Guanosine kinase activity was identified in an alkalophile, Exiguobact erium aurantiacum ATCC 35652, and the gsk gene encoding it was isolate d as a homologous fragment of the Brevibacterium acetylicum gsk. The c loned chromosomal fragment contained an open reading frame which encod es a polypeptide of 308 amino acids with a molecular mass of 33 349 Da . The Ex. aurantiacum Gsk shows strong sequence similarity to B. acety licum Gsk, but possesses five additional amino acids at the C-terminus . An M-r 39 200 protein synthesized in Escherichia coli harboring plas mids carrying Ex. aurantiacum gsk was purified and characterized. A 0. 9 kb transcript revealed by Northern blot analysis and the presence of a factor-independent terminator structure suggest that Ex. aurantiacu m gsk is monocistronic, although B. acetylicum gsk has been shown to b e bicistronic. The striking alterations in the 3'-untranslated region resulted in a different gene organization. (C) 1998 Elsevier Science B .V. All rights reserved.