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bioRxiv · 10.1101/217323

A tangled tale of convergence and divergence: archaeal chromosomal proteins and Chromo-like domains in bacteria and eukaryotes

Kaur, G.·Iyer, L. M.·Subramanian, S.·Aravind, L.
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Abstract

The Chromo-like superfamily of SH3-fold {beta}-barrel domains recognize epigenetic marks in eukaryotic proteins. Their provenance has been placed either in archaea, based on apparent structural similarity to chromatin-compacting Sul7d and Cren7 proteins, or in bacteria based on the presence of sequence homologs. Using sequence and structural evidence we establish that the archaeal Cren7/Sul7 proteins emerged from a zinc ribbon (ZnR) ancestor. Further, we show that the ancestral eukaryotic Chromo-like domains evolved from bacterial precursors acquired from early endosymbioses, which already possessed an aromatic cage for recognition of modified amino-groups. These bacterial versions are part of a radiation of secreted SH3-fold domains, which spawned both chromo-like domains and classical SH3 domains in the context of peptide-recognition in the peptidoglycan. This establishes that Cren7/Sul7 converged to a \"SH3\"-like state from a ZnR precursor via the loss of metal-chelation and acquisition of stronger hydrophobic interactions; it is unlikely to have participated in the evolution of the chromo-like domains. We show that archaea possess several Cren7/Sul7-related proteins with intact Zn-chelating ligands, which we predict to play previously unstudied roles in cell-division comparable to the PRC barrel.

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Kaur, G., Iyer, L. M., Subramanian, S., Aravind, L.. 2017-11-10. A tangled tale of convergence and divergence: archaeal chromosomal proteins and Chromo-like domains in bacteria and eukaryotes. https://doi.org/10.1101/217323

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