Conformational changes of actin induced by calponin

“…The affinity of binding of calponin and actin is very high (Kd = 4.6 x 10-8 M) [9]. This strong binding causes conformational changes in actin protomers that seems to be responsible for the reduction of their interaction with myosin heads [13].…”

Section: Introductionmentioning

confidence: 99%

Interaction of calponin with actin and its functional implications

Kolakowski

Makuch

Stȩpkowski

et al. 1995

Biochemical Journal

View full text Add to dashboard Cite

Titration of F-actin with calponin causes the formation of two types of complexes. One, at saturation, contains a lower ratio of calponin to actin (0.5:1) and is insoluble at physiological ionic strength. The another is soluble, with a higher ratio of calponin to actin (1:1). Electron microscopy revealed that the former complex consists of paracrystalline bundles of actin filaments, whereas the latter consists of separate filaments. Ca(2+)-calmodulin causes dissociation of bundles with simultaneous increase in the number of separate calponin-containing filaments. Further increase in the calmodulin concentration results in full release of calponin from actin filaments. In motility assays, calponin, when added together with ATP to actin filaments complexed with immobilized myosin, evoked a decrease in both the number and velocity of moving actin filaments. Addition of calponin to actin filaments before their binding to myosin resulted in a formation of actin filament bundles which were dissociated by ATP.

show abstract

“…In addition, a non-muscle acidic isoform of calponin with distinct functional properties has recently been described (33). Several findings suggest that calponin may regulate SMC contraction: (i) calponin binds to the thin filament proteins actin, tropomyosin, calmodulin, and caltropin (34 -38), (ii) calponin can reversibly inhibit the actinactivated myosin MgATPase (39,40), (iii) calponin can inhibit the Ca 2ϩ -dependent mobility of actin on immobilized myosin (41), (iv) calponin induces conformational changes in F-actin (42), and (v) calponin decreases the rate of cross-bridge cycling and increases maximum force production by smooth muscle myosin (43). Despite these in vitro findings, the molecular mechanism by which calponin regulates smooth muscle cell contraction in vivo remains unknown.…”

mentioning

confidence: 99%

Developmental Pattern of Expression and Genomic Organization of the Calponin-h1 Gene

Samaha¹,

Ip²,

Morrisey

et al. 1996

Journal of Biological Chemistry

104

View full text Add to dashboard Cite

Calponin-h1 is a 34-kDa myofibrillar thin filament, actin-binding protein that is expressed exclusively in smooth muscle cells (SMCs) in adult animals. To examine the molecular mechanisms that regulate SMC-specific gene expression, we have examined the temporal, spatial, and cell cycle-regulated patterns of expression of calponin-h1 gene expression and isolated and structurally characterized the murine calponin-h1 gene. Calponin-h1 mRNA is expressed exclusively in SMC-containing tissues in adult animals. During murine embryonic development, calponin-h1 gene expression is (i) detectable in E9.5 embryos in the dorsal aorta, cardiac outflow tract, and tubular heart, (ii) sequentially up-regulated in SMC-containing tissues, and (iii) downregulated to non-detectable levels in the heart during late fetal development. In addition, the gene is expressed in resting rat aortic SMCs, but its expression is rapidly down-regulated when growth-arrested cells reenter phase G 1 of the cell cycle and proliferate. Calponin-h1 is encoded by a 10.7-kilobase single copy gene composed of seven exons, which is part of a multigene family. Transient transfection analyses demonstrated that 1.5 kilobases of calponin-h1 5-flanking sequence is sufficient to program high level transcription of a luciferase reporter gene in cultured primary rat aortic SMCs and the smooth muscle cell line, A7r5. Taken together, these data suggest that the calponin-h1 gene will serve as an excellent model system with which to examine the molecular mechanisms that regulate SMC lineage specification, differentiation, and phenotypic modulation.

show abstract

Conformational changes of actin induced by calponin

Cited by 30 publications

References 15 publications

Functional Analysis of Rat Acidic Calponin.

Functional Analysis of Rat Acidic Calponin.

Interaction of calponin with actin and its functional implications

Developmental Pattern of Expression and Genomic Organization of the Calponin-h1 Gene

Contact Info

Product

Resources

About