Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.4.4 (kinesin)
 5,033 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calponin is a basic smooth muscle protein capable of binding to actin, calmodulin, tropomyosin, and phospholipids. We have found that the basic calponin interacted with brain tubulin under polymerized and unpolymerized conditions in vitro [Fujii, T., Hiromori, T., Hamamoto, M., and Suzuki, T. (1997) J. Biochem. 122, 344-351]. We examined the calponin-binding site on the tubulin molecule by sedimentation, limited digestion, chemical-cross linking, immunoblotting, and delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometric (DE MALDI-TOF) analyses. Calponin interacts with both the alpha and beta tubulins and only slightly with the tyrosinated and acetylated form of alpha tubulin. The binding of calponin to microtubules was blocked by adding poly(L-aspartic acid) (PLAA) or MAP2. After digestion of microtubule proteins with subtilisin, the amount of calponin binding to alphabetas microtubules was reduced compared to native microtubules, but no further reduction was observed in the case of alphasbetas microtubules. The chemical cross-linked products of calponin and synthesized peptides (KDYEEVGVDSVEGE; alpha-KE) derived from the C-terminal region of alpha tubulin and (YQQYQDATADEQG; beta-YG) and (GEFEEEGEEDEA; beta-GA) from that of beta tubulin were detected by mass spectrometry. One kind of calponin-peptide complex was formed in the presence of alpha-KE or beta-YG, while five complexes (calponin:peptide = 1:1-5) were generated in the presence of beta-GA. Peptides alpha-KE and beta-GA inhibited the binding of calponin to tubulin produced by EDC in a concentration-dependent manner. These findings suggest that basic calponin interacts with both tubulin subunits and that their C-terminal regions, which also contain the binding sites of MAP2, tau, and kinesin, may be involved in calponin-binding.
 ...
PMID:Identification of the binding region of basic calponin on alpha and beta tubulins. 1022 May 77

The smooth muscle basic calponin interacts with F-actin and inhibits the actomyosin ATPase in a calmodulin or phosphorylation modulated manner. It also binds in vitro to microtubules and its acidic isoform, present in nonmuscle cells, and co-localizes with microfilaments and microtubules in cultured neurons. To assess the physiological significance and the molecular basis of the calponin-microtubule interaction, we have first studied the solution binding of recombinant acidic calponin to microtubules using quantitative cosedimentation analyses. We have also characterized, for the first time, the ability of both calponin isoforms to induce the inhibition of the microtubule-stimulated ATPase activity of the cytoskeletal, kinesin-related nonclaret dysjunctional motor protein (ncd) and the abolition of this effect by calcium calmodulin. This property makes calponin a potent inhibitor of all filament-activated motor ATPases and, therefore, a potential regulatory factor of many motor-based biological events. By combining the enzymatic measurements of the ncd-microtubules system with various in vitro binding assays employing proteolytic, recombinant and synthetic fragments of basic calponin, we further unambiguously identified the interaction of microtubules at two distinct calponin sites. One is inhibitory and resides in the segment 145-182, which also binds F-actin and calmodulin. The other one is noninhibitory, specific for microtubules, and is located on the COOH-terminal repeat-containing region 183-292. Finally, quantitative fluorescence studies of the binding of basic calponin to the skeletal pyrenyl F-actin in the presence of microtubules did not reveal a noticeable competition between the two sets of filaments for calponin. This result implies that calponin undergoes a concomitant binding to both F-actin and microtubules by interaction at the former site with actin and at the second site with microtubules. Thus, in the living cells, calponin could potentially behave as a cross-linking protein between the two major cytoskeletal filaments.
 ...
PMID:Mapping the microtubule binding regions of calponin. 1256 30