Substrate specificity of adenovirus protease

The adenovirus protease, adenain is functionally required for virion uncoating and virion maturation and release from the infected cell. In addition to hydrolysis of precursor proteins at specific consensus sites, adenain has also been observed to cleave viral proteins at other sites. Here we re-examine the sequences in the consensus sites and also the phenomena of cleavage at other sites on viral proteins 11, 100K, V, VI and VII. An examination of the eight residues flanking the scissile bond in 274 consensus sites from 36 different adenovirus scrotypes in the DNA sequence databanks provided the following main conclusions: (1) two types of consensus sites, type 1, (M,I,L)XGX-G and type 2, (M,I,L)XGG-X, (2) the variant positions P-3 and P(1)never contained C,P,D,H,W,Y and C,P,G,M amino acids, respectively in type 1, (3) the variant positions P-3 and P-1 never contained C,D,L,W and C,P,D,Q,H,Y,W amino acids, respectively in type 2, and (4) the thiol forming C residue occurred only twice within the eight residues flanking the scissile bond and that in the P position. Six unusual serotypes had (M,L,I)XAT-G as the PVII consensus site. Adenain has been proposed to cleave protein VI at an unknown site in the course of virion uncoating. The cleavage of capsid protein VI in the absence of a consensus site is confirmed here in vitro using recombinant adenain. Virion proteins 11, V and VII and the nonstructural protein 100K were also digested in vitro into discrete fragments by recombinant adenain. We conclude that adenain preferentially cleaves viral proteins at their consensus sites, but is capable, in vitro of cleavages at other discrete sites which resemble the consensus cleavage sites. (C) 2002 Elsevier Science B.V. All rights reserved.