Functional implications of hexameric assembly of RraA proteins from Vibrio vulnificus

Abstract

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.

Heat Stress in Legume Seed Setting: Effects, Causes, and Future Prospects

“…The late embryogenesis abundant (LEA) proteins have been shown to be related to desiccation tolerance (Boudet et al, 2006). Stress-related genes have been profiled (Shu et al, 2013; Song et al, 2015, 2017; Albornos et al, 2017), and myo-inositol and proline have been shown to be involved in Medicago drought tolerance (Zhang et al, 2014). The salinity tolerance is related to the induction and expression of highly regulated antioxidant mechanisms (Mhadhbi et al, 2011).…”

Identification of the global regulatory roles of RraA via the integrative transcriptome and proteome in Vibrio alginolyticus

“…Furthermore, no variations were observed in either swimming or swarming motility among the strains ( Fig. 2C ), which contrasts with the decreases in swimming and swarming motility observed in the RraAV1 mutant strain of V. vulnificus ( 12 , 24 ).…”

“…It has been reported that the overexpression of RraAV1 results in a moderately slower growth rate than that of the WT in V. vulnificus ( 7 , 24 ). However, in the present study, changes in the rraA transcript abundance did not significantly affect the growth of LBS in rich media ( Fig.…”