posted on 2020-03-10, 15:07authored byPatrick McConnell, Marlene Mekel, Alexander G. Kozlov, Olivia L. Mooren, Timothy M. Lohman, John A. Cooper
The heterodimeric actin capping protein
(CP) is regulated by a
set of proteins that contain CP-interacting (CPI) motifs. Outside
of the CPI motif, the sequences of these proteins are unrelated and
distinct. The CPI motif and surrounding sequences are conserved within
a given protein family, when compared to those of other CPI-motif
protein families. Using biochemical assays with purified proteins,
we compared the ability of CPI-motif-containing peptides from different
protein families (a) to bind to CP, (b) to allosterically inhibit
barbed-end capping by CP, and (c) to allosterically inhibit interaction
of CP with V-1, another regulator of CP. We found large differences
in potency among the different CPI-motif-containing peptides, and
the different functional assays showed different orders of potency.
These biochemical differences among the CPI-motif peptides presumably
reflect interactions between CP and CPI-motif peptides involving amino
acid residues that are conserved but are not part of the strictly
defined consensus, as it was originally identified in comparisons
of sequences of CPI motifs across all protein families [Hernandez-Valladares,
M., et al. (2010) Structural characterization of a capping protein
interaction motif defines a family of actin filament regulators. Nat. Struct. Mol. Biol. 17, 497–503; Bruck, S., et
al. (2006) Identification of a Novel Inhibitory Actin-capping Protein
Binding Motif in CD2-associated Protein. J. Biol. Chem. 281, 19196–19203]. These biochemical differences may be important
for conserved distinct functions of CPI-motif protein families in
cells with respect to the regulation of CP activity and actin assembly
near membranes.