Cross-Linked Dimers with Nucleating Activity in Actin Prepared from Muscle Acetone Powder

详细信息    查看全文

• 作者：Lynn A. Selden ; Henry J. Kinosian ; James E. Estes ; and Lewis C. Gershman
• 刊名：Biochemistry
• 出版年：2000
• 出版时间：January 11, 2000
• 年：2000
• 卷：39
• 期：1
• 页码：64 - 74
• 全文大小：182K
• 年卷期：v.39,no.1(January 11, 2000)
• ISSN：1520-4995

文摘

A covalently linked actin dimer is identified in solutions of actin prepared from an acetonepowder from skeletal muscle. This actin dimer acts as an actin nucleating factor (ANF), decreasing thehalf-time for spontaneous actin polymerization. ANF reacts with antibodies to both the N- and C-terminalportions of actin on Western blots and migrates during reduced polyacrylamide gel electrophoresis likeactin cross-linked with N,N'-p-phenylenebismaleimide. The origin of the cross-linked dimer appears tobe related to the presence of carbonyl groups in purified actin. A large number of carbonyls (~0.3/actin)are introduced into actin during the prolonged treatment with acetone in the preparation of the muscleacetone powder from which actin is extracted. Actin extracted from acetone powder prepared by a singleacetone wash and actin prepared from bovine spleen, which is not washed with acetone, both containfewer carbonyl groups (~0.05 carbonyl/actin). ANF forms spontaneously in solutions of polymer actincontaining 0.3 carbonyl/actin. We speculate that a reaction between a carbonyl on one actin polymersubunit and a lysine on a neighboring subunit is responsible for ANF formation. The presence of cross-linked actin dimers in commonly used skeletal muscle actin preparations could certainly affect studies ofactin polymerization and, particularly, studies of the nucleation reaction. The physiological relevance ofANF is not clear, but given the large cellular concentration of actin, similar reactions yielding ANF couldoccur in vivo when increased levels of reactive oxygen species are present.