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A Bonet-Kerrache

Publications and source records attributed to A Bonet-Kerrache.

13 recordsLinked to original sources
PubMed2001

Neurocalcin-actin interaction.

Neurocalcin is an N-myristoylated calcium-binding protein which belongs to a novel family of neuronal calcium sensors. Here we show, by cosedimentation, co-immunoprecipitation and cross-linking approaches, that myristoylated neurocalcin directly interacts with actin in a calcium-dependent manner. We used EDC cross-linking and obtained one novel 64 kDa entity composed of one actin molecule and one neurocalcin molecule, as demonstrated with IAEDANS-actin and neurocalcin-specific antibodies. This interaction could modulate the rod outer segment-guanylate cyclase 1-neurocalcin interface.

Actins↗
PubMed1999

Dystrophin and utrophin complexed with different associated proteins in cardiac Purkinje fibres.

Abnormal dystrophin expression is directly responsible for Duchenne and Becker muscular dystrophies. In skeletal muscle, dystrophin provides a link between the actin network and the extracellular matrix via the dystrophin-associated protein complex. In mature skeletal muscle, utrophin is a dystrophin-related protein localized mainly at the neuromuscular junction, with the same properties as dystrophin in terms of linking the protein complex. Utrophin could potentially overcome the absence of dystrophin in dystrophic skeletal muscles. In cardiac muscle, dystrophin and utrophin were both found to be present with a distinct subcellular distribution in Purkinje fibres, i.e. utrophin was limited to the cytoplasm, while dystrophin was located in the cytoplasmic membrane. In this study, we used this particular characteristic of cardiac Purkinje fibres and demonstrated that associated proteins of dystrophin and utrophin are different in this structure. We conclude, contrary to skeletal muscle, dystrophin-associated proteins do not form a complex in Purkinje fibres. In addition, we have indirect evidence of the presence of two different 400 kDa dystrophins in Purkinje fibres.

Animals↗
PubMed1999

Utrophin and dystrophin-associated glycoproteins in normal and dystrophin deficient cardiac muscle.

In this study, various members of the dystrophin family (dystrophin, the short dystrophin product Dp 71, utrophin and DRP2), and different members of the dystrophin-associated glycoprotein (DAG) complex (beta-dystroglycan, alpha-, beta-, gamma- and delta-sarcoglycans) were localized in bovine cardiac muscle using a battery of specific antibodies. We have established that dystrophin is exclusively associated with beta-dystroglycan and both alpha- and delta-sarcoglycans in cardiac muscle cell membranes. In contrast, utrophin is a specific component of intercalated disks together with beta- and gamma-sarcoglycans, while beta-dystroglycan, alpha- and delta-sarcoglycans are not present. Dp 71 is mainly localized at the T tubule transverse area. In dystrophin deficient cardiac muscle, utrophin and beta-sarcoglycan were observed in intercalated disks and at the sarcolemma of each cardiocyte. Our results revealed that complexes of associated glycoproteins differ in cardiac muscle when associated with dystrophin or utrophin. Despite the described sequence homologies between dystrophin and utrophin, the present results indicate that these proteins have different roles in some specific cardiac cell areas.

Amino Acid Sequence↗
PubMed1995

Dystrophin, the protein that promotes membrane resistance.

Deficiency of dystrophin, a 427-kDa subsarcolemma membrane protein, is responsible for Duchenne muscular dystrophy. The function of this protein is not clear but its subcellular distribution suggests that it is an important link between the cytoskeleton and the extracellular matrix, thus maintaining membrane integrity. The N-terminus of dystrophin was shown to bind actin in vivo and in vitro via two major actin binding sites. The role of dystrophin/actin interactions has been investigated and the results presented here demonstrate for the first time that the N-terminal part of dystrophin is able (i) to interact with G-actin monomers, and (ii) to slowly promote G->F actin transformation. This conversion was shown to be stimulated the presence of calmodulin in a calcium dependent manner. This is evidence that dystrophin is an anchor protein for actin involved in the control of membrane cell shape deformation and developing a calmodulin-calcium induced F-actin network, thus stiffening the myotube membrane cytoskeleton.

Actins↗
PubMed1995

The binding of distinct segments of actin to multiple sites in the C-terminus of caldesmon: comparative aspects of actin interaction with troponin-I and caldesmon.

Thin-filament-based regulation of the contractile response is considered to involve the interaction of actin with troponin-I in striated muscle and the interaction of actin with caldesmon in smooth muscle. The nature of the interaction with actin of these inhibitory proteins has been studied by proton magnetic resonance spectroscopy using segments of caldesmon and troponin-I which mimic their functional properties. Caldesmon is shown to interact with two distinct sites on the N-terminal residues 1-44 of actin subdomain 1 with corresponding contacts on caldesmon domain 3 and domain 4 at its C-terminus. We demonstrate that, whereas inhibition by the troponin-I fragment (residues 96-117) is effected by its interaction with the N-terminal region of actin, the separate inhibitory ability of different regions of the C-terminus of caldesmon (domains 4a and 4b) is mediated by interaction with noncontiguous segments on subdomain 1 of actin. Our studies of the spatial relationship of these actin contacts on caldesmon further suggest that one molecule of caldesmon may associate with two actin monomers. The demonstrated interactive nature of these caldesmon attachments to distinct regions of actin is relevant to the mechanism of calcium modulation of inhibition of actomyosin ATPase by caldesmon.

Actins↗
PubMed1995

Importance of the C-terminal part of actin in interactions with calponin.

Native, modified or trypsin-truncated actin was used to study the impact of modifying the C-terminal part of actin (the last three amino acids) on interactions with calponin. We used three different techniques to show that these amino acids are essential for the actin-calponin interface. The locations of actin-calponin interaction sites on the actin crystal are discussed in terms of previously reported data.

Actins↗
PubMed1994

N-terminal domain of dystrophin.

Contro-versial experiments have been published on calmodulin binding of dystrophin. In this study, we used recombinant proteins and the techniques of affinity chromatography and ELISA to show that the N-terminal part of dystrophin binds calmodulin specifically in a calcium-dependent manner. The calcium-dependent interaction of calmodulin and dystrophin does not directly regulate binding of actin to dystrophin, but may regulate dystrophin interactions with other associated proteins.

Actins↗
PubMed1994

Purification and properties of caldesmon-like protein from molluscan smooth muscle.

In this comparative study, the heat-stable protein content of scallop muscles was reinvestigated. The hCaD-like protein was prepared and its properties carefully examined. The heat-stable high-molecular-mass caldesmon-like (hCaD-like) protein is only present in the catch (smooth) muscle and it is completely absent in the striated muscle of scallop. The isolated scallop hCaD-like protein cosediments with F-actin, binds to myosin significantly and inhibits the ATPase activity of acto-myosin. A partial cDNA clone from a Mytilus anterior byssus retractor muscle (ABRM)-related protein showed strong homology with the hCaD gizzard sequence. This allowed identification of the heat-stable 100-110 kDa protein doublet band isolated in this study as a caldesmon-like molecule.

Amino Acid Sequence↗
PubMed1993

Actin-dystrophin interface.

Dystrophin, an elongated cytoskeletal molecule which is deficient in Duchenne muscular disease, contains an actin-binding domain in its N-terminal portion. We show that this part interacted with actin in the native molecule. By molecular biology techniques, four recombinant proteins were expressed in Escherichia coli using the pMAL vector which allowed us to obtain soluble proteins directly after purification. These constructions were tested for their ability to bind actin under various conditions, and their apparent dissociation constants were determined. The effects of other actin-binding proteins such as caldesmon and tropomyosin were analyzed in comparison to the actin-binding properties of these constructions. These results support the potential concept of a multiple actin-binding contact in the N-terminal region of dystrophin. Differences in the functional domains are discussed relative to similar alpha-actinin-actin-binding sites.

Actins↗
PubMed1991

Actin-caldesmon-myosin-subfragment-1 ternary complex viewed by electron microscopy. Competitive actin binding region for caldesmon and myosin subfragment-1.

An earlier electron microscopic study using different caldesmon forms complexed with actin revealed that the aggregates produced display regular periodic striation after antibody labeling of the 35-kDa caldesmon fragment. This approach provides further evidence that a caldesmon fragment, even as small as 15 kDa, can induce actin filaments to assemble into bundles. The observed difference in the compactness of these structures, depending on the use of the 15-kDa fragment instead of the 35-kDa fragment, suggests the existence of more than one actin-binding site in the caldesmon molecule. In this study, the caldesmon-induced process of F-actin association was investigated in the presence of skeletal myosin subfragment-1, using light-scattering methods, cosedimentation experiment and electron microscopic techniques. We show that the actin-caldesmon association is partially destabilized in the presence of subfragment-1 and this leads to a ternary complex formation. Immunogold labelling of the actin filaments still reveals the presence of caldesmon within this structure. This latter result strengthens the hypothesis that actin has a site(s) able to bind both caldesmon and myosin subfragment-1, as detected by recent NMR observations. This evidence is discussed with respect to the regulatory function of caldesmon during smooth muscle contraction.

Actins↗
PubMed1990

New subfragment 1 of skeletal muscle myosin obtained by thrombin cleavage.

The head of the myosin molecule (i.e., subfragment 1 with a heavy chain of 95 kDa) is usually obtained by chymotryptic cleavage in the presence of a divalent cation chelator. In the present work, we used another specific proteolytic enzyme, thrombin, to produce a limited cut within the myosin molecule, resulting in a new species of N-terminal fragment. Treatment of skeletal muscle myosin yielded a 97-kDa split heavy chain associated with intact light chains, corresponding to a single cut. The ATPase activities of this new S-1 derivative were slightly affected by the breakdown. It recognized actin in an ATP-dependent manner, as expected, with an affinity 2-5 times higher than that of the usual chymotryptic S-1 preparation but with a very different electron microscopic pattern. Functional differences are noted, and we involve them more precisely in relation to possible structural aspects of the additional C-terminal segment extending the usual S-1 heavy chain from 95 to 97 kDa.

Actins↗