Origin of viruses: primordial replicators recruiting capsids from hosts

Submarine hydrothermal vents are geochemically reactive habitats that harbour rich microbial communities. There are striking parallels between the chemistry of the H(2)-CO(2) redox couple that is present in hydrothermal systems and the core energy metabolic reactions of some modern prokaryotic autotrophs. The biochemistry of these autotrophs might, in turn, harbour clues about the kinds of reactions that initiated the chemistry of life. Hydrothermal vents thus unite microbiology and geology to breathe new life into research into one of biology's most important questions - what is the origin of life?

The RNA recognition motif (RRM) is one of the most abundant protein domains in eukaryotes. While the structure of this domain is well characterized by the packing of two alpha-helices on a four-stranded beta-sheet, the mode of protein and RNA recognition by RRMs is not clear owing to the high variability of these interactions. Here we report recent structural data on RRM-RNA and RRM-protein interactions showing the ability of this domain to modulate its binding affinity and specificity using each of its constitutive elements (beta-strands, loops, alpha-helices). The extreme structural versatility of the RRM interactions explains why RRM-containing proteins have so diverse biological functions.