title: The C terminus of formin FMNL3 accelerates actin polymerization and contains a WH2 domain-like sequence that binds both monomers and filament barbed ends.
abstract: Formin proteins are actin assembly factors that accelerate filament nucleation then remain on the elongating barbed end and modulate filament elongation. The formin homology 2 (FH2) domain is central to these activities, but recent work has suggested that additional sequences enhance FH2 domain function. Here we show that the C-terminal 76 amino acids of the formin FMNL3 have a dramatic effect on the ability of the FH2 domain to accelerate actin assembly. This C-terminal region contains a WASp homology 2 (WH2)-like sequence that binds actin monomers in a manner that is competitive with other WH2 domains and with profilin. In addition, the C terminus binds filament barbed ends. As a monomer, the FMNL3 C terminus inhibits actin polymerization and slows barbed end elongation with moderate affinity. As a dimer, the C terminus accelerates actin polymerization from monomers and displays high affinity inhibition of barbed end elongation. These properties are not common to all formin C termini, as those of mDia1 and INF2 do not behave similarly. Interestingly, mutation of two aliphatic residues, which blocks high affinity actin binding by the WH2-like sequence, has no effect on the ability of the C terminus to enhance FH2-mediated polymerization. However, mutation of three successive basic residues at the C terminus of the WH2-like sequence compromises polymerization enhancement. These results illustrate that the C termini of formins are highly diverse in their interactions with actin.
authors.affiliation: Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
authors.forename: Ernest G
authors.initials: EG
authors.lastname: Heimsath
authors.forename: Henry N
authors.initials: HN
authors.lastname: Higgs
mesh_terms: D008841:Actin Cytoskeleton / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D000818:Animals; D000080865:Formins; D051379:Mice; D020125:Mutation, Missense; D011485:Protein Binding; D055503:Protein Multimerization / Q000502:physiology*; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; C570808:FMNL3 protein, mouse; D000080865:Formins; D011506:Proteins
references.citation: Curr Biol. 2006 Oct 10;16(19):1924-30
references.pmid: 17027489
references.citation: Cell. 2006 Jan 27;124(2):423-35
references.pmid: 16439214
references.citation: Nat Struct Mol Biol. 2011 Aug 28;18(9):1068-74
references.pmid: 21873984
references.citation: Annu Rev Biochem. 2001;70:649-76
references.pmid: 11395419
references.citation: Ann N Y Acad Sci. 2010 Apr;1194:44-52
references.pmid: 20536449
references.citation: J Biol Chem. 2006 May 19;281(20):14383-92
references.pmid: 16556604
references.citation: Proc Natl Acad Sci U S A. 2005 Nov 15;102(46):16644-9
references.pmid: 16275905
references.citation: J Biol Chem. 2008 Nov 28;283(48):33750-62
references.pmid: 18835814
references.citation: J Cell Sci. 2009 May 1;122(Pt 9):1430-40
references.pmid: 19366733
references.citation: J Biol Chem. 2004 May 7;279(19):20076-87
references.pmid: 14990563
references.citation: Nature. 2005 Jan 27;433(7024):382-8
references.pmid: 15674283
references.citation: Nat Rev Mol Cell Biol. 2010 Apr;11(4):237-51
references.pmid: 20237478
references.citation: Biochemistry. 1984 Dec 18;23(26):6631-41
references.pmid: 6543322
references.citation: J Mol Biol. 2007 Jun 22;369(5):1258-69
references.pmid: 17482208
references.citation: Science. 2001 Jul 27;293(5530):708-11
references.pmid: 11474115
references.citation: J Biol Chem. 2006 Sep 8;281(36):26754-67
references.pmid: 16818491
references.citation: J Biol Chem. 2005 Feb 25;280(8):6986-92
references.pmid: 15591319
references.citation: J Mol Biol. 2011 Apr 22;408(1):18-25
references.pmid: 21315084
references.citation: J Biol Chem. 1971 Aug 10;246(15):4866-71
references.pmid: 4254541
references.citation: Biophys J. 2005 Feb;88(2):1387-402
references.pmid: 15556992
references.citation: Genes Cells. 2007 Nov;12(11):1255-65
references.pmid: 17986009
references.citation: Biochemistry. 1999 Nov 16;38(46):15212-22
references.pmid: 10563804
references.citation: Cell. 1980 Jun;20(2):329-41
references.pmid: 6893016
references.citation: Cell. 2007 Oct 19;131(2):337-50
references.pmid: 17956734
references.citation: Cytoskeleton (Hoboken). 2010 Dec;67(12):755-72
references.pmid: 20862687
references.citation: Nature. 1993 Oct 28;365(6449):810-6
references.pmid: 8413665
references.citation: Mol Cell. 2007 Nov 30;28(4):555-68
references.pmid: 18042452
references.citation: Cell. 2004 May 28;117(5):611-23
references.pmid: 15163409
references.citation: Structure. 2007 Feb;15(2):145-55
references.pmid: 17292833
references.citation: Proc Natl Acad Sci U S A. 2007 Oct 23;104(43):17117-22
references.pmid: 17942696
references.citation: Trends Cell Biol. 2004 Jul;14(7):386-94
references.pmid: 15246432
references.citation: Curr Biol. 2003 Aug 5;13(15):1335-40
references.pmid: 12906795
references.citation: Nature. 2005 Feb 3;433(7025):488-94
references.pmid: 15635372
references.citation: Nat Struct Mol Biol. 2011 Aug 28;18(9):1060-7
references.pmid: 21873985
references.citation: Cell. 2004 Mar 5;116(5):711-23
references.pmid: 15006353
references.citation: Annu Rev Biochem. 2007;76:593-627
references.pmid: 17373907
references.citation: Nat Cell Biol. 2007 Oct;9(10):1110-21
references.pmid: 17909522
references.citation: Curr Biol. 2011 Mar 8;21(5):384-90
references.pmid: 21333540
references.citation: Mol Biol Cell. 2005 Jan;16(1):1-13
references.pmid: 15509653
references.citation: Cell. 2007 Mar 9;128(5):901-13
references.pmid: 17350575
references.citation: Crit Rev Biochem Mol Biol. 2009 Nov-Dec;44(6):351-66
references.pmid: 19874150
references.citation: Mol Cell. 2011 Aug 5;43(3):464-77
references.pmid: 21816349