3B5U

Actin filament model from extended form of acromsomal bundle in the Limulus sperm

Summary for 3B5U

• Entry DOI: 10.2210/pdb3b5u/pdb
• Related: 1ATN
• EMDB information: 1088
• Descriptor: Actin, alpha skeletal muscle (1 entity in total)
• Functional Keywords: actin filament, actin, acromsomal bundle, cryoem, motor protein
• Biological source: Oryctolagus cuniculus (rabbit)
• Total number of polymer chains: 14
• Total formula weight: 589357.34

Authors

Cong, Y.,Topf, M.,Sali, A.,Matsudaira, P.,Dougherty, M.,Chiu, W.,Schmid, M.F. (deposition date: 2007-10-26, release date: 2008-04-15, Last modification date: 2024-02-21)

Primary citation

Cong, Y.,Topf, M.,Sali, A.,Matsudaira, P.,Dougherty, M.,Chiu, W.,Schmid, M.F.
Crystallographic conformers of actin in a biologically active bundle of filaments
J.Mol.Biol., 375:331-336, 2008

PubMed Abstract: Actin carries out many of its cellular functions through its filamentous form; thus, understanding the detailed structure of actin filaments is an essential step in achieving a mechanistic understanding of actin function. The acrosomal bundle in the Limulus sperm has been shown to be a quasi-crystalline array with an asymmetric unit composed of a filament with 14 actin-scruin pairs. The bundle in its true discharge state penetrates the jelly coat of the egg. Our previous electron crystallographic reconstruction demonstrated that the actin filament cross-linked by scruin in this acrosomal bundle state deviates significantly from a perfect F-actin helix. In that study, the tertiary structure of each of the 14 actin protomers in the asymmetric unit of the bundle filament was assumed to be constant. In the current study, an actin filament atomic model in the acrosomal bundle has been refined by combining rigid-body docking with multiple actin crystal structures from the Protein Data Bank and constrained energy minimization. Our observation demonstrates that actin protomers adopt different tertiary conformations when they form an actin filament in the bundle. The scruin and bundle packing forces appear to influence the tertiary and quaternary conformations of actin in the filament of this biologically active bundle.

PubMed: 18022194
DOI: 10.1016/j.jmb.2007.10.027

Experimental method

ELECTRON CRYSTALLOGRAPHY (9.5 Å)