Determination of the alpha-actinin-binding site on actin filaments by cryoelectron microscopy and image analysis.
The three-dimensional structure of actin filaments decorated with the actin-binding domain of chick smooth muscle alpha-actinin (alpha A1-2) has been determined to 21-A resolution. The shape and location of alpha A1-2 was determined by subtracting maps of F-actin from the reconstruction of decorated filaments. alpha A1-2 resembles a bell that measures approximately 38 A at its base and extends 42 A from its base to its tip. In decorated filaments, the base of alpha A1-2 is centered about the outer face of subdomain 2 of actin and contacts subdomain 1 of two neighboring monomers along the long-pitch (two-start) helical strands. Using the atomic model of F-actin (Lorenz, M., D. Popp, and K. C. Holmes. 1993. J. Mol. Biol. 234:826-836.), we have been able to test directly the likelihood that specific actin residues, which have been previously identified by others, interact with alpha A1-2. Our results indicate that residues 86-117 and 350-375 comprise distinct binding sites for alpha-actinin on adjacent actin monomers.
Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254.
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McGough
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D008841:Actin Cytoskeleton / Q000737:chemistry / Q000648:ultrastructure; D000185:Actinin / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D000199:Actins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D001665:Binding Sites; D002645:Chickens; D003196:Computer Graphics; D005583:Fourier Analysis; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008854:Microscopy, Electron / Q000379:methods; D015394:Molecular Structure; D009132:Muscles / Q000737:chemistry; D011487:Protein Conformation
D000199:Actins; D000185:Actinin