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== Publication Abstract from PubMed ==

Activating signal cointegrator-1 homology (ASCH) domains were initially reported in human as a part of the ASC-1 transcriptional regulator, a component of a putative RNA-interacting protein complex; their presence has now been confirmed in a wide range of organisms. Here, we have determined the trigonal and monoclinic crystal structures of an ASCH domain-containing protein from Zymomonas mobilis (ZmASCH), and analyzed the structural determinants of its nucleic acid processing activity. The protein has a central beta-barrel structure with several nearby alpha-helices. Positively charged surface patches form a cleft that runs through the pocket formed between the beta-barrel and the surrounding alpha-helices. We further demonstrate by means of in vitro assays that ZmASCH binds nucleic acids, and degrades single-stranded RNAs in a magnesium ion-dependent manner with a cleavage preference for the phosphodiester bond between the pyrimidine and adenine nucleotides. ZmASCH also removes a nucleotide at the 5'-end. Mutagenesis studies, guided by molecular dynamics simulations, confirmed that three residues (Tyr47, Lys53, and Ser128) situated in the cleft contribute to nucleic acid-binding and RNA cleavage activities. These structural and biochemical studies imply that prokaryotic ASCH may function to control the cellular RNA amount.

Crystal structure of an ASCH protein from Zymomonas mobilis and its ribonuclease activity specific for single-stranded RNA.,Kim BN, Shin M, Ha SC, Park SY, Seo PW, Hofmann A, Kim JS Sci Rep. 2017 Sep 26;7(1):12303. doi: 10.1038/s41598-017-12186-w. PMID:28951575<ref>PMID:28951575</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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