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The mysterious RAMP proteins and their roles in small RNA‐based immunity
Author(s) -
Wang Ruiying,
Li Hong
Publication year - 2012
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.2044
Subject(s) - immunity , rna , biology , computational biology , microbiology and biotechnology , genetics , immune system , gene
Abstract A new class of prokaryotic RNA binding proteins called Repeat Associated Mysterious Proteins (RAMPs), has recently been identified. These proteins play key roles in a novel type immunity in which the DNA of the host organism (e.g. a prokaryote) has sequence segments corresponding to the sequences of potential viral invaders. The sequences embedded in the host DNA confer immunity by directing selective destruction of the nucleic acid of the virus using an RNA‐based strategy. In this viral defense mechanism, RAMP proteins have multiple functional roles including endoribonucleotic cleavage and ribonucleoprotein particle assembly. RAMPs contain the classical RNA recognition motif (RRM), often in tandem, and a conserved glycine‐rich segment (G‐loop) near the carboxyl terminus. However, unlike RRMs that bind single‐stranded RNA using their β‐sheet surface, RAMPs make use of both sides of the RRM fold and interact with both single‐stranded and structured RNA. The unique spatial arrangement of the two RRM folds, facilitated by a hallmark G‐loop, is crucial to formation of a composite surface for recognition of specific RNA. Evidence for RNA‐dependent oligomerization is also observed in some RAMP proteins that may serve as an important strategy to increase specificity.