Arch Virol (2000) 145: 1473–1479
Conformational changes during proteolytic processing
of a picornavirus capsid proteins
M. S. Smyth
, A. Trudgett
, J. H. Martin
, E. M. Hoey
, and S. J. Martin
Department of Biochemistry, University of Leicester, Leicester, U.K.
School of Biology and Biochemistry, Queen’s University of Belfast, Belfast, U.K.
Division of Biomedical Sciences, School of Health Sciences,
University of Wolverhampton, Wolverhampton, U.K.
Accepted February 15, 2000
Summary. We have used synthetic peptide antibodies to probe conformational
changes that occur during the cleavage cascade which generates the capsid pro-
teins of a picornavirus. The initial translation product of 97 kDa, the precursor
of all four structural proteins, is cleaved to form a 63 kDa fragment which, we
show, has signiﬁcantly different folding characteristics to both its larger parent
and its products. We demonstrate that proteolytic cleavages as distant as 520
residues from epitopes confer sufﬁciently large conformational changes as to
render them unrecognisable. To our knowledge, this is the ﬁrst demonstration of
this phenomenon in the picornavirus system.
Post translational proteolytic processing is a key factor in major enzymic and
structural systems, such as the maturation of mammalian digestive proteases and
viral capsid protein production. In terms of the structure-function relationship,
these cleavages must be accompanied by major conformational changes. To inves-
tigate this, we have used synthetic peptide antibodies to probe the conformational
changes during the maturation of picornavirus capsid proteins.
Picornaviruses are among the smallest and structurally most economical ani-
mal pathogens . The non-enveloped capsid, approximately 300 Å in diameter,
comprises 60 copies of each of four proteins, 1A, 1B, 1C and 1D (VP4, 2, 3 and
1), arranged in icosahedral pseudo T = 3 symmetry . The genome is a single
molecule of message sense RNA on average 7500 bases in length .
Immediately following uncoating, the genome is translated in a single open
reading frame to yield a polyprotein potentially in excess of 200 kDa . The