Arch Virol (1999) 144: 1173–1189
Three epitopes located on the coat protein amino terminus
of viruses in the bean common mosaic potyvirus subgroup
G. I. Mink
, H. J. Vetten
, S. D. Wyatt
, P. H. Berger
, and M. J. Silbernagel
Washington State University, WSU-Prosser, Washington, U.S.A.
Institute of Biochemistry and Plant Virology, Braunschweig, Germany
Washington State University, Department of Plant Pathology,
Pullman, Washington, U.S.A.
University of Idaho, Department of Plant, Soil and Entomological Sciences,
Moscow, Idaho, U.S.A.
US Department of Agriculture, Agriculture Research Service,
Prosser, Washington, U.S.A.
Accepted October 26, 1998
Summary. Twenty-seven of 29 strains of viruses in the bean common mosaic
virus (BCMV) subgroup of legume-infecting potyviruses reacted strongly with
one or more of the monoclonal antibodies (MAbs) which are known to be speciﬁc
for epitopes located along the 50 amino acids which constitute the N-terminal end
of the viral coat protein. Approximately one half of the virus strains reacted with
the N-terminal epitope speciﬁc (NTES) MAb 4G12 which is speciﬁc for epitope
for epitope E/B3. All but two strains contained at least one of these epitopes
while no strain contained both. Competitive assays using ﬁve sequential, non-
overlapping, synthetic, 10mer peptides indicated that the amino acids critical for
epitope E/B3 reaction were located at positions 5, 7, and 10 from the N-terminal
end of the coat protein. By deduction we postulate that the amino acids critical
for epitope E/B4 are located at positions 10, 16, and 17. Because epitope E/B3
requires isoleucine at position 10 for expression whereas epitope E/B4 requires
valine to be expressed, no one strain can express both epitopes. Two viruses in our
tests (azuki mosaic and Dendrobium mosaic viruses) had deletions in this portion
of their sequence explaining their failure to react MAbs speciﬁc for either epitope.
The critical amino acids for a third epitope, E/B3A, were located at positions 16
and 17. We found no correlation between any of the three N-terminal epitopes
deﬁned in this study and the presence or absence of any biological property that
we could accurately measure: i.e., symptomatology, host range, or pathotype.
However, when coat protein sequences were aligned according to epitope type
E/B3 or E/B4, we found that sequences within groups had high levels of identity