Characterization of Protospacer Adjacent Motifs in a Type I-B CRISPR system of Thermotoga maritima

In conjunction with their associated (Cas) proteins, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) represent a number of prokaryotic genome defense systems present in virtually all archaea, and approximately half of all bacteria. CRISPR-Cas systems provide these microorganisms with adaptable heritable immunity against foreign genetic elements, primarily phage DNA. It is well documented that short conserved sequences named protospacer adjacent motifs (PAMs) are critical for identification of foreign DNA targets in many CRISPR systems. Here an in vitro plasmid based interference assay using purified recombinant proteins was exploited to identify and characterize the protospacer adjacent motifs associated with a Type I-B CRISPR system from the hyperthermophile Thermotoga maritima