TABLE 1.
Biochemical activities and cellular localization of yeast actin-binding proteins
| Name | Homologue(s) | Localization | Classa | Actin binding (Kd) | Activities and functions | Key references |
|---|---|---|---|---|---|---|
| Abp1 | mAbp1 | Patches | F | Filament sides (∼0.6 μM) | Activates Arp2/3 complex; links Srv2 and Ark1/Prk1 to patches | 84, 127, 307 |
| Abp140 | Unknown | Patches, cables | F | Filament sides | Bundles filaments; Abp140-GFP is used as a cable marker | 17, 419 |
| Aip1 | Aip1 | Patches | F | Caps barbed ends | Promotes filament disassembly by enhancing cofilin severing and capping cofilin-severed filaments | 274, 275, 317 |
| Arp2/3 complex | Arp2/3 complex | Patches | F | Filament sides (∼2 μM)b; pointed ends (∼20 nM)b | Nucleates filaments and promotes filament branching; requires activation by NPFs (Las17, Pan1, Myo3, Myo5, and Abp1) | 127, 313, 406, 408 |
| Bni1 | Formin | Bud tip and neck | F | Barbed ends (∼7 nM)c | Nucleates filaments; processively caps barbed ends | 303, 326, 414 |
| Bnr1 | Formin | Bud neck | F | Barbed ends (<1 nM)c | Nucleates and bundles filaments; processively caps barbed ends | 251, 304 |
| Cap1/Cap2 | Capping protein | Patches | F | Caps barbed ends (∼10 nM) | Caps barbed ends and stabilizes filaments | 11, 415 |
| Crn1 | Coronin | Patches | F | Filament sides (∼6 nM) | Cross-links and bundles filaments; recruits Arp2/3 to sides of filaments and restricts nucleation activity to sides | 128, 161 |
| Iqg1/Cyk1 | IQGAP | Bud neck | F | Filament sides | IQGAP bundles filaments and is regulated by Cdc42 and calmodulin | 26, 114, 341 |
| Myo3 | Myosin type I | Patches | F | F-actin motor | Activates Arp2/3 complex; may promote vesicle scission in endocytosis; regulated by phosphorylation of TEDS motif | 172, 210, 411 |
| Myo5 | Myosin type I | Patches | F | F-actin motor | Same as Myo3 | See Myo3 |
| Myo1 | Myosin type II | Bud neck | F | F-actin motor | Recruits filaments and promotes closure of cytokinetic ring | 34, 217 |
| Myo2 | Myosin type V | Bud tip and neck | F | F-actin motor | Nonprocessive motor; transports vesicles and organelles to bud tip; facilitates mitotic spindle orientation with Kar9 and Bim1 | 171, 310, 421 |
| Myo4 | Myosin type V | Bud tip and neck | F | F-actin motor | Transports daughter-specific mRNAs to bud tip (e.g., Ash1) | 40, 310 |
| Pan1 | Eps15 | Patches | F | Filament sides (∼1 μM) | Activates Arp2/3 complex; binds filaments via atypical WH2 domain; phosphoregulated by Prk1 kinase | 87, 371 |
| Sac6 | Fimbrin | Patches, cables | F | Filament sides (∼0.5 μM)b | Bundles and stabilizes filaments | 4, 198 |
| Scp1 | Calponin/transgelin | Patches | F | Filament sides (∼1 μM) | Bundles and stabilizes filaments | 129, 405 |
| Sla2 | HIP1R | Patches | F | Filament sides | Binds PIP2, clathrin, may bundle filaments; HIP1R promotes clathrin assembly | 240, 360 |
| Tpm1 | Tropomyosin | Cables | F | Filament sides (∼2 μM) | Stabilizes filaments; competes with cofilin for filament binding | 61, 81, 219, 220 |
| Tpm2 | Tropomyosin | Cables | F | Filament sides | Same as Tpm1 | 61, 81 |
| Bud6/Aip3 | Unknown | Bud tip and neck | G | ATP-G-actin (∼0.75 μM)c | Stimulates Bni1-mediated actin assembly; promotes nucleotide exchange on actin monomers | 14, 253 |
| Las17/Bee1 | WASp | Patches | G | Binds monomers | Activates Arp2/3 complex; inhibited by Sla1 and Bbc1 | 315, 406 |
| Pfy1 | Profilin | Cytoplasmic | G | ATP-G-actin (∼0.1 μM)b; ADP-G-actin (∼0.5 μM)b | Promotes nucleotide exchange on actin monomers; inhibits spontaneous actin assembly; restricts growth to barbed ends of filaments | 88, 225, 410 |
| Srv2 | Cyclase-associated protein (CAP) | Patches | G | ATP-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-actin | 23, 214, 237, 249 |
| Cof1 | Cofilin | Patches | F, G | Filament sides (∼1 μM); ATP-G-actin (∼2 μM)b; ADP-G-actin (∼0.1 μM)b | Severs/disassembles filaments; inhibits nucleotide exchange on monomers | 204, 205 |
| Twf1 | Twinfilin | Patches | F, G | ADP-G-actin (∼50 nM); filament sides | Sequesters monomers; severs filaments at low pH; regulated by binding to Cap1/Cap2 and PIP2 | 125, 252, 285 |
| Vrp1 | WASp-interacting protein (WIP) | Patches | F, G | WIP binds filaments and monomers | Binds Las17 and myosin type I; unknown biochemical function | 151, 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.