THE RNASE P RNA FROM CYANOBACTERIA - SHORT TANDEMLY REPEATED REPETITIVE (STRR) SEQUENCES ARE PRESENT WITHIN THE RNASE P RNA GENE IN HETEROCYST-FORMING CYANOBACTERIA

摘要

The RNase P RNA gene (rnpB) from 10 cyanobacteria has been characterized, These new RNAs, together with the previously available ones, provide a comprehensive data set of RNase P RNA from diverse cyanobacterial lineages, All heterocystous cyanobacteria, but none of the non-heterocystous strains analyzed, contain short tandemly repeated repetitive (STRR) sequences that increase the length of helix P12, Site-directed mutagenesis experiments indicate that the STRR sequences are not required for catalytic activity in vitro, STRR sequences seem to have recently and independently invaded the RNase P RNA genes in heterocyst-forming cyanobacteria because closely related strains contain unrelated STRR sequences. Most cyanobacteria RNase P RNAs lack the sequence GGU in the loop connecting helices P15 and P16 that has been established to interact with the 3'-end CCA in precursor tRNA substrates in other bacteria, This character is shared with plastid RNase P RNA, Helix P6 is longer than usual in most cyanobacteria as well as in plastid RNase P RNA.