IS1626, a new IS900-related Mycobacterium avium insertion sequence

An insertion sequence designated IS1626 was isolated and characterized from a Mycobacterium avium clinical strain. IS1626 was detected by high-stringe ncy hybridization with the pMB22/S12 probe from IS900 of Mycobacterium para tuberculosis. IS1626 is 1418 bp in size and has a G+C content of 65 mol%. I t has neither terminal inverted repeats nor flanking direct repeats. Analys is of three IS1626 insertion sites in the M. avium strain and the correspon ding potential insertion sites in two IS1626-free M. avium strains indicate d a consensus sequence of CATGCN((4-5))TCCTN((2))G for IS1626 insertion. In the three clones examined, IS1626 has the same orientation with respect to this target site. IS1626 has two major ORFs. ORF1179 encodes a predicted p rotein of 393 amino acids. ORF930, on the complementary strand of ORF1179, encodes a protein of 310 amino acids. The Shine-Dalgarno sequence for ORF93 0 is partially located in the flanking region, similar to other IS900-relat ed elements. Analysis of the comparable features of insertion sequences and their variable occurrence in related organisms is useful for studying the evolution of these elements and their hosts.