The C terminus of annexin II mediates binding to F-actin.
Annexin II heterotetramer (AIIt) is a multifunctional Ca(2+)-binding protein composed of two 11-kDa subunits and two annexin II subunits. The annexin II subunit contains the binding sites for anionic phospholipids, heparin, and F-actin, whereas the p11 subunit provides a regulatory function. The F-actin-binding site is presently unknown. In the present study we have utilized site-directed mutagenesis to create annexin II mutants with truncations in the C terminus of the molecule. Interestingly, a mutant annexin II lacking its C-terminal 16, 13, or 9 amino acids was unable to bind to F-actin but still retained its ability to interact with both anionic phospholipids and heparin. Recombinant AIIt, composed of wild-type p11 subunits and the mutant annexin II subunits, was also unable to bundle F-actin. This loss of F-actin bundling activity was directly attributable to the inability of mutant AIIt to bind F-actin. These results establish for the first time that the annexin II C-terminal amino acid residues, LLYLCGGDD, participate in F-actin binding.
Filipenko
N R
NR
Cancer Biology Research Group, Department of Biochemistry, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
Waisman
D M
DM
D000199:Actins / Q000378:metabolism*; D020816:Amino Acid Motifs; D000818:Animals; D017306:Annexin A2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010743:Phospholipids / Q000378:metabolism
D000199:Actins; D017306:Annexin A2; D010743:Phospholipids