SIGNATURE SEQUENCES IN DIVERSE PROTEINS PROVIDE EVIDENCE OF A CLOSE EVOLUTIONARY RELATIONSHIP BETWEEN THE DEINOCOCCUS-THERMUS GROUP AND CYANOBACTERIA

A number of proteins have been identified that contain prominent seque nce signatures that are uniquely shared by the members of the Deinococ cus-Thermus genera and the cyanobacterial species but which are not fo und in any of the other eubacterial or archaebacterial homologs. The p roteins containing such sequence signatures include (1) the DnaJ/Hsp40 family of proteins, (2) DNA polymerase I, (3) the protein synthesis e longation factor EF-Tu, and (4) the elongation factor EF-Ts. A strong affinity of the Deinococcus-Thermus species to cyanobacteria is also s een in the phylogenetic trees based on Hsp70 and DnaJ sequences. These results provide strong evidence of a close and specific evolutionary relationship between species belonging to these two eubacterial divisi ons.