期刊
RNA BIOLOGY
卷 12, 期 7, 页码 749-760出版社
TAYLOR & FRANCIS INC
DOI: 10.1080/15476286.2015.1051300
关键词
Archaeoglobus fulgidus Csx3; CRISPR; Cas; deadenylation exonuclease; ferredoxin-like fold; manganese-dependent
资金
- Singapore Ministry of Education [MOE2014-T2-1-103]
- Natural Science Foundation in Jiangsu Province [BK20131189]
- National University of Singapore (Suzhou) Research Institute [R-2012-N-007]
In prokaryotes, the CRISPR/Cas system is known to target and degrade invading phages and foreign genetic elements upon subsequent infection. However, the structure and function of many Cas proteins remain largely unknown, due to the high diversity of Cas proteins. Here we report 3 crystal structures of Archaeoglobus fulgidus Csx3 (AfCsx3) in free form, in complex with manganese ions and in complex with a single-stranded RNA (ssRNA) fragment, respectively. AfCsx3 harbors a ferredoxin-like fold and forms dimer both in the crystal and in solution. Our structure-based biochemical analysis demonstrates that the RNA binding sites and cleavage sites are located at 2 separate surfaces within the AfCsx3 dimer, suggesting a model to bind, tether and cleave the incoming RNA substrate. In addition, AfCsx3 displays robust 3-deadenylase activity in the presence of manganese ions, which strongly suggests that AfCsx3 functions as a deadenylation exonuclease. Taken together, our results indicate that AfCsx3 is a Cas protein involved in RNA deadenylation and provide a framework for understanding the role of AfCsx3 in the Type III-B CRISPR/Cas system.
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