Novel molecular aspects of the CRISPR backbone protein 'Cas7' from cyanobacteria.

Novel molecular aspects of the CRISPR backbone protein 'Cas7' from cyanobacteria. Biochem J. 2020 Mar 13;477(5):971-983 Authors: Kalwani P, Rath D, Ballal A Abstract The cyanobacterium Anabaena PCC 7120 shows the presence of Type I-D CRISPR system that can potentially confer adaptive immunity. The Cas7 protein (Alr1562), which forms the backbone of the type I-D surveillance complex, was characterized from Anabaena. Alr1562, showed the presence of the non-canonical RNA recognition motif and two intrinsically disordered regions (IDRs). When overexpressed in E. coli, the Alr1562 protein was soluble and could be purified by affinity chromatography, however, deletion of IDRs rendered Alr1562 completely insoluble. The purified Alr1562 was present in the dimeric or a RNA-associated higher oligomeric form, which appeared as spiral structures under electron microscope. With RNaseA and NaCl treatment, the higher oligomeric form converted to the lower oligomeric form, indicating that oligomerization occurred due to the association of Alr1562 with RNA. The secondary structure of both these forms was largely similar, resembling that of a partially folded protein. The dimeric Alr1562 was more prone to temperature-dependent aggregation than the higher oligomeric form. In vitro, the Alr1562 bound more specifically to a minimal CRISPR unit than to the non-specific RNA. Residues required for binding of Alr1562 to RNA, identified by protein modeling-ba...
Source: The Biochemical Journal - Category: Biochemistry Authors: Tags: Biochem J Source Type: research