RESUMEN
The structure of the X (or ADRP) domain of a pathogenic variant of feline coronavirus (FCoV) has been determined in tetragonal and cubic crystal forms to 3.1 and 2.2 A resolution, respectively. In the tetragonal crystal form, glycerol-3-phosphate was observed in the ADP-ribose-binding site. Both crystal forms contained large solvent channels and had a solvent content of higher than 70%. Only very weak binding of this domain to ADP-ribose was detected in vitro. However, the structure with ADP-ribose bound was determined in the cubic crystal form at 3.9 A resolution. The structure of the FCoV X domain had the expected macro-domain fold and is the first structure of this domain from a coronavirus belonging to subgroup 1a.
Asunto(s)
Coronavirus Felino/enzimología , Dominios y Motivos de Interacción de Proteínas , ARN Polimerasa Dependiente del ARN/química , Proteínas no Estructurales Virales/química , Adenosina Difosfato Ribosa/química , Adenosina Difosfato Ribosa/metabolismo , Secuencia de Aminoácidos , Sitios de Unión , Cristalografía por Rayos X , Glicerofosfatos/química , Glicerofosfatos/metabolismo , Datos de Secuencia Molecular , Unión Proteica , Alineación de Secuencia , Homología de Secuencia de AminoácidoRESUMEN
The polyproteins of coronaviruses are cleaved by viral proteases into at least 15 nonstructural proteins (Nsps). Consisting of five domains, Nsp3 is the largest of these (180-210 kDa). Among these domains, the so-called X-domain is believed to act as ADP-ribose-1''-phosphate phosphatase or to bind poly(ADP-ribose). However, here we show that the X-domain of Infectious Bronchitis Virus (strain Beaudette), a Group-3 coronavirus, fails to bind ADP-ribose. This is explained on the basis of the crystal structure of the protein, determined at two different pH values. For comparison, we also describe the crystal structure of the homologous X-domain from Human Coronavirus 229E, a Group-1 coronavirus, which does bind ADP-ribose.