In vitro characterization of native mammalian smooth-muscle protein synaptopodin 2.
An analysis of the primary structure of the actin-binding protein fesselin revealed it to be the avian homologue of mammalian synaptopodin 2 [Schroeter, Beall, Heid, and Chalovich (2008) Biochem. Biophys. Res. Commun. 371, 582-586]. We isolated two synaptopodin 2 isoforms from rabbit stomach that corresponded to known types of human synaptopodin 2. The purification scheme used was that developed for avian fesselin. These synaptopodin 2 forms shared several key functions with fesselin. Both avian fesselin and mammalian synaptopodin 2 bound to Ca(2+)-calmodulin, alpha-actinin and smooth-muscle myosin. In addition, both proteins stimulated the polymerization of actin in a Ca(2+)-calmodulin-dependent manner. Synaptopodin 2 has never before been shown to polymerize actin in the absence of alpha-actinin, to polymerize actin in a Ca(2+)-calmodulin-dependent manner, or to bind to Ca(2+)-calmodulin or myosin. These properties are consistent with the proposed function of synaptopodin 2 in organizing the cytoskeleton.
Schroeter
Mechthild M
MM
Department of Biochemistry and Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, NC 27834, USA. schroeterm@ecu.edu
Beall
Brent
B
Heid
Hans W
HW
Chalovich
Joseph M
JM
D000185:Actinin / Q000378:metabolism; D000818:Animals; D002147:Calmodulin / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D009124:Muscle Proteins / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism*; D009130:Muscle, Smooth / Q000737:chemistry / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D011817:Rabbits
D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009124:Muscle Proteins; C503979:SYNPO2 protein, human; C443099:fesselin; D000185:Actinin; D009218:Myosins