K. Miyazaki et al., PHYSARUM VITRONECTIN-LIKE PROTEIN HAS EXTENSIVE HOMOLOGY TO DIHYDROLIPOAMIDE ACETYLTRANSFERASE, Cell structure and function, 18(5), 1993, pp. 323-331
Physarum vitronectin-like protein with a molecular mass of 70 kDa cros
s-reacts with antibovine vitronectin and promotes cell-spreading (Miya
zaki, K. et al. 1992. Exp. Cell Res., 199: 106-110.). The amino-termin
al sequence of Physarum vitronectin-like protein is, however, distinct
from those of animal vitronectins but shows significant sequence homo
logy with dihydrolipoamide acetyltransferase, a component of pyruvate
dehydrogenase complex. We have investigated the structural relationshi
ps between Physarum vitronectin-like protein and dihydrolipoamide acet
yltransferase by using both antibody and protein-chemical methods. The
vitronectin-like protein reacted with both anti-bovine vitronectin Ig
G and anti-rat pyruvate dehydrogenase complex IgG, indicating that it
shares common antigenic determinant(s) with rat pyruvate dehydrogenase
complex. Furthermore, sequencing studies of peptides obtained by lysy
lendopeptidase digestion indicated that internal sequences of Physarum
vitronectin-like protein show significant homology with dihydrolipoam
ide acetyltransferase, but do not show any homology with the primary s
tructures of authentic vitronectins. Immunocytochemistry revealed that
the protein is widely localized in cytoplasm and nuclei of Physarum p
olycephalum, but is not present in the central area of vacuoles. Our r
esults indicate that Physarum vitronectin-like protein is a molecule s
tructurally and immunologically related to dihydrolipoamide acetyltran
sferase but functionally similar to animal vitronectin, although its l
ocalization is unique.