Mc. Hart et al., VERTEBRATES HAVE CONSERVED CAPPING PROTEIN ALPHA-ISOFORMS WITH SPECIFIC EXPRESSION PATTERNS, Cell motility and the cytoskeleton, 38(2), 1997, pp. 120-132
Capping protein (CP), a ubiquitous actin binding protein composed of a
n alpha and a beta subunit, is important for actin assembly and fell m
otility. Lower organisms have one gene and one isoform of each subunit
. Chickens have two very similar alpha-subunit isoforms. To determine
if vertebrates in general contain multiple alpha isoforms and If those
alpha isoforms have conserved sequences, we isolated and analyzed alp
ha subunit cDNA's in mice and humans, Both mice and humans also have t
wo alpha isoforms. Phylogenetic analysis of the alpha isoform sequence
s reveals that vertebrates have two highly conserved subfamilies, alph
a 1 and alpha 2. The alpha 1 and alpha 2 subfamilies are very similar
to each other but can be defined and distinguished from each other by
a small number of key amino acid residues, In addition, 3' untranslate
d cDNA sequences are conserved within the isoform subfamilies. To inve
stigate the function of the alpha isoforms, we examined their expressi
on In mouse cells and tissues. Endothelial cells contain only the alph
a 2 isoform, and erythrocytes contain almost exclusively the alpha 1 i
soform, Most tissues have both alpha 1 and alpha 2 isoforms but the ra
tio of alpha 1:alpha 2 varies widely. Together, these findings support
the hypothesis that the CP alpha isoforms have conserved, unique and
essential roles in vertebrates. (C) 1997 Wiley-Liss, Inc.