Structural and biochemical studies on a hypothetical protein PYCH_01220 from Pyrococcus yayanosii

Abstract

Hypothetical protein is a protein which is translated from the open reading frame but its biological function or mechanism is unknown. Herein, we report the crystal structure of one of the hypothetical proteins, PYCH_01220 in Pyrococcus yayanosii CH1. This protein is composed of two domains, named Domain A and Domain B. While Domain B is not significantly homologous to any of known protein structures, Domain A is structurally analogous to the C-terminal ribonuclease domain of Escherichia coli colicin D. Domain A has a positively charged surface patch rendered by 13 basic residues, eight arginine or lysine residues of which are evolutionarily conserved. Electrophoretic mobility shift assays showed that PYCH_01220 binds to DNA, and charge-inversion mutations on this patch negatively affect the DNA binding, suggesting that the function of PYCH_01220 might involve nucleic acid-binding via the positively charged patch.