The V-ATPase subunit C binds to polymeric F-actin as well as to monomeric G-actin and induces cross-linking of actin filaments

Autor(en): Vitavska, O 
Merzendorfer, H 
Wieczorek, H 
Stichwörter: ANIMAL PLASMA-MEMBRANE; Biochemistry & Molecular Biology; BUNDLING ACTIVITY; CYTOSKELETON; IN-VIVO; PROTEINS; PURIFICATION; SITE; TOBACCO HORNWORM MIDGUT; TWINFILIN
Erscheinungsdatum: 2005
Herausgeber: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Journal: JOURNAL OF BIOLOGICAL CHEMISTRY
Volumen: 280
Ausgabe: 2
Startseite: 1070
Seitenende: 1076
Zusammenfassung: 
Previously, we have shown that the V-ATPase holoenzyme as well as the V-1 complex isolated from the midgut of the tobacco hornworm ( Manduca sexta) exhibits the ability of binding to actin filaments via the V-1 subunits B and C (Vitavska, O., Wieczorek, H., and Merzendorfer, H. (2003) J. Biol. Chem. 278, 18499 - 18505). Since the recombinant subunit C not only enhances actin binding of the V-1 complex but also can bind separately to F-actin, we analyzed the interaction of recombinant subunit C with actin. We demonstrate that it binds not only to F-actin but also to monomeric G-actin. With dissociation constants of similar to 50 nM, the interaction exhibits a high affinity, and no difference could be observed between binding to ATP-G-actin or ADP-G-actin, respectively. Unlike other proteins such as members of the ADF/cofilin family, which also bind to G- as well as to F-actin, subunit C does not destabilize actin filaments. On the contrary, under conditions where the disassembly of F-actin into G- actin usually occurred, subunit C stabilized F-actin. In addition, it increased the initial rate of actin polymerization in a concentration-dependent manner and was shown to cross-link actin filaments to bundles of varying thickness. Apparently bundling is enabled by the existence of at least two actin-binding sites present in the N- and in the C-terminal halves of subunits C, respectively. Since subunit C has the possibility to dimerize or even to oligomerize, spacing between actin filaments could be variable in size.
ISSN: 00219258
DOI: 10.1074/jbc.M406797200

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