Identification and functional analysis of RNase E of Vibrio angustum S14 and two-hybrid analysis of its interaction partners

RNase E is an essential enzyme that catalyses RNA processing. Microdomains which mediate interactions between RNase E and other members of the degradosome have been defined. To further elucidate the role of these microdomains in molecular interactions, we studied RNase E from Vibrio angustum S14. Protein sequence analysis revealed that its C-terminal half is less conserved and structured than its N-terminal half. Within this structural disorder, however, exist five small regions of predicted structural propensity. Four are similar to interaction-mediating microdomains identified in other RNase E proteins; the fifth did not correspond to any known functional motif. The function of the V. angustum S14 enolase-binding microdomain was confirmed using bacterial two-hybrid analysis, demonstrating the conserved function of this microdomain for the first time in a species other than Escherichia coli. Further, PNPase in V. angustum S14 was shown to interact with the last 80 amino acids of the C-terminal region of RNase E. This raises the possibility that PNPase interacts with the small ordered region at residues 1026–1041. The role of RNase E as a hub protein and the implications of microdomain-mediated interactions in relation to specificity and function are discussed.