Open AccessFunctional implications of hexameric assembly of RraA proteins from Vibrio vulnificus
Author(s) -
Saemee Song,
Seokho Hong,
Jinyang Jang,
Ji-Hyun Yeom,
Nohra Park,
Jaejin Lee,
Yeri Lim,
Jun-Yeong Jeon,
HyungKyoon Choi,
Minho Lee,
NamChul Ha,
Kangseok Lee
Publication year - 2017
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0190064
Subject(s) - vibrio vulnificus , rnase p , escherichia coli , biochemistry , rna , oligomer , biology , ribonuclease iii , ribonucleoprotein , chemistry , microbiology and biotechnology , bacteria , genetics , gene , rna interference , organic chemistry
RNase E has a pivotal role in the degradation and processing of RNAs in Escherichia coli , and protein inhibitors RraA and RraB control its enzymatic activity. The halophilic pathogenic bacterium Vibrio vulnificus also expresses orthologs of RNase E and RraA—RNase EV, RraAV1, and RraAV2 (herein renamed as VvRNase E, VvRraA1, and VvRraA2). A previous study showed that VvRraA1 actively inhibits the ribonucleolytic activity of VvRNase E by interacting with the C-terminal region of VvRNase E. However, the molecular mechanism underlying the effect of VvRraA1 on the ribonucleolytic activity of VvRNase E has not yet been elucidated. In this study, we report that the oligomer formation of VvRraA proteins affects binding efficiency to VvRNase E as well as inhibitory activity on VvRNase E action. The hexameric structure of VvRraA1 was converted to lower oligomeric forms when the Cys 9 residue was substituted with an Asp residue (VvRraA1-C9D), showing decreased inhibitory activity of VvRraA1 on VvRNase E in vivo . These results indicated that the intermolecular disulfide linkage contributed critically to the hexamerization of VvRraA1 for its proper function. On the contrary, the VvRraA2 that existed in a trimeric state did not bind to or inhibit VvRNase E. An in vitro cleavage assay further showed the reduced inhibitory effect of VvRraA-C9D on VvRNase E activity compared to wild-type VvRraA1. These findings provide insight into how VvRraA proteins can regulate VvRNase E action on its substrate RNA in V . vulnificus . In addition, based on structural and functional comparison of RraA homologs, we suggest that hexameric assembly of RraA homologs may well be required for their action on RNase E-like proteins.