Chimeric and truncated gCap39 elucidate the requirements for actin filament severing and end capping by the gelsolin family of proteins

Fu Xin Yu, Deming Zhou, Helen L. Yin

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

gCap39 is an actin filament end-capping protein which has a threefold repeated domain structure similar to the N-terminal half of gelsolin. However, unlike gelsolin, gCap39 does not sever actin filaments and dissociates completely from filament ends after calcium removal. We have capitalized on these differences to explore the structural basis for actin filament capping, severing, and their regulation. Using truncated gCap39, generated by limited proteolysis or deletion mutagenesis, we found that actin filament capping requires multiple gCap domains, and almost the entire molecule is necessary for optimal activity. gCap39 domain I, like the equivalent domain in gelsolin, contains an actin monomer binding site. gCap39 domains II-III are, however, different from gelsolin in that they do not bind to the side of actin filaments. Since filament side binding is hypothesized to be the first step in severing, lack of side binding may explain why gCap39 does not sever. This is confirmed directly by swapping gCap39 domains II-III for the side-binding gelsolin domains to generate a chimera which severs actin filaments. The chimera is Ca2+ independent in actin filament severing and capping, although gCap39 domain I itself is regulated by Ca2+.

Original languageEnglish (US)
Pages (from-to)19269-19275
Number of pages7
JournalJournal of Biological Chemistry
Volume266
Issue number29
StatePublished - Oct 15 1991

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Gelsolin
Actin Cytoskeleton
Actins
Proteins
Actin Capping Proteins
Proteolysis
Mutagenesis
Binding Sites
Calcium
Monomers
Molecules

ASJC Scopus subject areas

  • Biochemistry

Cite this

Chimeric and truncated gCap39 elucidate the requirements for actin filament severing and end capping by the gelsolin family of proteins. / Yu, Fu Xin; Zhou, Deming; Yin, Helen L.

In: Journal of Biological Chemistry, Vol. 266, No. 29, 15.10.1991, p. 19269-19275.

Research output: Contribution to journalArticle

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AB - gCap39 is an actin filament end-capping protein which has a threefold repeated domain structure similar to the N-terminal half of gelsolin. However, unlike gelsolin, gCap39 does not sever actin filaments and dissociates completely from filament ends after calcium removal. We have capitalized on these differences to explore the structural basis for actin filament capping, severing, and their regulation. Using truncated gCap39, generated by limited proteolysis or deletion mutagenesis, we found that actin filament capping requires multiple gCap domains, and almost the entire molecule is necessary for optimal activity. gCap39 domain I, like the equivalent domain in gelsolin, contains an actin monomer binding site. gCap39 domains II-III are, however, different from gelsolin in that they do not bind to the side of actin filaments. Since filament side binding is hypothesized to be the first step in severing, lack of side binding may explain why gCap39 does not sever. This is confirmed directly by swapping gCap39 domains II-III for the side-binding gelsolin domains to generate a chimera which severs actin filaments. The chimera is Ca2+ independent in actin filament severing and capping, although gCap39 domain I itself is regulated by Ca2+.

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