The Saccharomyces cerevisiae calponin/transgelin homolog Scp1 functions with fimbrin to regulate stability and organization of the actin cytoskeleton.
Calponins and transgelins are members of a conserved family of actin-associated proteins widely expressed from yeast to humans. Although a role for calponin in muscle cells has been described, the biochemical activities and in vivo functions of nonmuscle calponins and transgelins are largely unknown. Herein, we have used genetic and biochemical analyses to characterize the budding yeast member of this family, Scp1, which most closely resembles transgelin and contains one calponin homology (CH) domain. We show that Scp1 is a novel component of yeast cortical actin patches and shares in vivo functions and biochemical activities with Sac6/fimbrin, the one other actin patch component that contains CH domains. Purified Scp1 binds directly to filamentous actin, cross-links actin filaments, and stabilizes filaments against disassembly. Sequences in Scp1 sufficient for actin binding and cross-linking reside in its carboxy terminus, outside the CH domain. Overexpression of SCP1 suppresses sac6Delta defects, and deletion of SCP1 enhances sac6Delta defects. Together, these data show that Scp1 and Sac6/fimbrin cooperate to stabilize and organize the yeast actin cytoskeleton.
Goodman
Anya
A
Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA.
Goode
Bruce L
BL
Matsudaira
Paul
P
Fink
Gerald R
GR
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000595:Amino Acid Sequence; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D000096985:Calponins
D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; D009124:Muscle Proteins; D029701:Saccharomyces cerevisiae Proteins; D000096985:Calponins; C483531:SCP1 protein, S cerevisiae; C058992:Tagln protein, mouse; C026742:plastin; C051615:transgelin