TABLE 1.

Biochemical activities and cellular localization of yeast actin-binding proteins

NameHomologue(s)LocalizationClassaActin binding (Kd)Activities and functionsKey references
Abp1mAbp1PatchesFFilament sides (∼0.6 μM)Activates Arp2/3 complex; links Srv2 and Ark1/Prk1 to patches84, 127, 307
Abp140UnknownPatches, cablesFFilament sidesBundles filaments; Abp140-GFP is used as a cable marker17, 419
Aip1Aip1PatchesFCaps barbed endsPromotes filament disassembly by enhancing cofilin severing and capping cofilin-severed filaments274, 275, 317
Arp2/3 complexArp2/3 complexPatchesFFilament sides (∼2 μM)b; pointed ends (∼20 nM)bNucleates filaments and promotes filament branching; requires activation by NPFs (Las17, Pan1, Myo3, Myo5, and Abp1)127, 313, 406, 408
Bni1ForminBud tip and neckFBarbed ends (∼7 nM)cNucleates filaments; processively caps barbed ends303, 326, 414
Bnr1ForminBud neckFBarbed ends (<1 nM)cNucleates and bundles filaments; processively caps barbed ends251, 304
Cap1/Cap2Capping proteinPatchesFCaps barbed ends (∼10 nM)Caps barbed ends and stabilizes filaments11, 415
Crn1CoroninPatchesFFilament sides (∼6 nM)Cross-links and bundles filaments; recruits Arp2/3 to sides of filaments and restricts nucleation activity to sides128, 161
Iqg1/Cyk1IQGAPBud neckFFilament sidesIQGAP bundles filaments and is regulated by Cdc42 and calmodulin26, 114, 341
Myo3Myosin type IPatchesFF-actin motorActivates Arp2/3 complex; may promote vesicle scission in endocytosis; regulated by phosphorylation of TEDS motif172, 210, 411
Myo5Myosin type IPatchesFF-actin motorSame as Myo3See Myo3
Myo1Myosin type IIBud neckFF-actin motorRecruits filaments and promotes closure of cytokinetic ring34, 217
Myo2Myosin type VBud tip and neckFF-actin motorNonprocessive motor; transports vesicles and organelles to bud tip; facilitates mitotic spindle orientation with Kar9 and Bim1171, 310, 421
Myo4Myosin type VBud tip and neckFF-actin motorTransports daughter-specific mRNAs to bud tip (e.g., Ash1)40, 310
Pan1Eps15PatchesFFilament sides (∼1 μM)Activates Arp2/3 complex; binds filaments via atypical WH2 domain; phosphoregulated by Prk1 kinase87, 371
Sac6FimbrinPatches, cablesFFilament sides (∼0.5 μM)bBundles and stabilizes filaments4, 198
Scp1Calponin/transgelinPatchesFFilament sides (∼1 μM)Bundles and stabilizes filaments129, 405
Sla2HIP1RPatchesFFilament sidesBinds PIP2, clathrin, may bundle filaments; HIP1R promotes clathrin assembly240, 360
Tpm1TropomyosinCablesFFilament sides (∼2 μM)Stabilizes filaments; competes with cofilin for filament binding61, 81, 219, 220
Tpm2TropomyosinCablesFFilament sidesSame as Tpm161, 81
Bud6/Aip3UnknownBud tip and neckGATP-G-actin (∼0.75 μM)cStimulates Bni1-mediated actin assembly; promotes nucleotide exchange on actin monomers14, 253
Las17/Bee1WASpPatchesGBinds monomersActivates Arp2/3 complex; inhibited by Sla1 and Bbc1315, 406
Pfy1ProfilinCytoplasmicGATP-G-actin (∼0.1 μM)b; ADP-G-actin (∼0.5 μM)bPromotes nucleotide exchange on actin monomers; inhibits spontaneous actin assembly; restricts growth to barbed ends of filaments88, 225, 410
Srv2Cyclase-associated protein (CAP)PatchesGATP-G-actin (∼1.9 μM); ADP-G-actin (∼20 nM)Oligomerizes to form high-molecular-mass complex (600 kDa) with actin monomers; blocks monomer addition to barbed ends; promotes conversion of cofilin-bound ADP-G-actin to profilin-bound ATP-G-actin23, 214, 237, 249
Cof1CofilinPatchesF, GFilament sides (∼1 μM); ATP-G-actin (∼2 μM)b; ADP-G-actin (∼0.1 μM)bSevers/disassembles filaments; inhibits nucleotide exchange on monomers204, 205
Twf1TwinfilinPatchesF, GADP-G-actin (∼50 nM); filament sidesSequesters monomers; severs filaments at low pH; regulated by binding to Cap1/Cap2 and PIP2125, 252, 285
Vrp1WASp-interacting protein (WIP)PatchesF, GWIP binds filaments and monomersBinds Las17 and myosin type I; unknown biochemical function151, 179, 234, 377, 382
  • a Proteins are listed alphabetically within three classes: binding to F-actin (F), binding to G-actin (G), and binding to both F-actin and G-actin (F, G).

  • b Kd derived for nonyeast homologue.

  • c Kd derived for yeast protein using nonyeast actin.