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Publication Abstract from PubMed

Clustered regularly interspaced short palindromic repeats (CRISPR) in many prokaryotes functions as an adaptive immune system against mobile genetic elements. A heterologous ribonucleoprotein silencing complex composed of CRISPR-associated (Cas) proteins and a CRISPR RNA (crRNA) neutralizes the incoming mobile genetic elements. The type I and III silencing complexes commonly include a protein-helical backbone of several copies of identical subunits, for example, Cas7 in the type I silencing complex. In this study, we structurally characterized type I-B Cas7 (Csh2 from Thermobaculum terrenum; TterCsh2). The revealed crystal structure of TterCsh2 shows a typical glove-like architecture of Cas7, which consists of a palm, a thumb, and a finger domain. Csh2 proteins have 5 conserved sequence motifs that are arranged to form a presumable crRNA-binding site in the TterCsh2 structure. This crRNA binding site of TterCsh2 is structurally and potentially comparable to those observed in helix-forming Cas7 structures in other sub-types. Analysis of the reported Cas7 structures and their sequences suggests that Cas7s can be divided into at least two sub-classes. These data will broaden our understanding on the Cascade complex of CRISPR/Cas systems.

Structural characterization of the type I-B CRISPR Cas7 from Thermobaculum terrenum.,Seo PW, Gu DH, Kim JW, Kim JH, Park SY, Kim JS Biochim Biophys Acta Proteins Proteom. 2023 May 1;1871(3):140900. doi: , 10.1016/j.bbapap.2023.140900. Epub 2023 Jan 20. PMID:36682394^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.