scholarly journals Chemical Modification of Vesamicol Binding Sites and Frequency Augmentation-Potentiation in Neuromuscular Transmission.

1994 ◽  
Vol 44 (6) ◽  
pp. 705-716 ◽  
Author(s):  
T. MAENO ◽  
K. ENOMOTO ◽  
M. SAWADA ◽  
M. ICHINOSE
Keyword(s):  
Chemical Modification ◽  
Binding Sites ◽  
Neuromuscular Transmission ◽  
Vesamicol Binding

N-Ethylmaleimide-modified actin filaments do not bundle in the presence of α-actinin

1995 ◽  
Vol 73 (1-2) ◽  
pp. 116-122 ◽  
Author(s):  
Aldo Milzani ◽  
Isabella DalleDonne ◽  
Roberto Colombo
Keyword(s):  
Polyethylene Glycol ◽  
Chemical Modification ◽  
Molecular Interactions ◽  
Binding Sites ◽  
Actin Filaments ◽  
Actin Assembly ◽  
Chemically Modified ◽  
C Terminus ◽  
Spatial Reorganization ◽  
Polyethylene Glycol 6000

We show that the modification of actin subdomain 1 by N-ethylmaleimide (NEM), which binds Cys-374 close to the C-terminus of the molecule, inhibits the α-actinin-induced bundling of actin filaments. This effect is not merely related to the block of Cys-374, since N-(1-pyrenyl)iodoacetamide (pyrene-IA) is unable to prevent bundling. Considering that NEM (but not pyrene-IA) influences actin assembly, we suggest that the inhibition of the actin – α-actinin interaction is due to the chemical modification of actin Cys-374 which, by inducing a marked spatial reorganization of actin monomers, is able to modify both the intra- and inter-molecular interactions of this protein. Finally, NEM-modified actin filaments form bundles in the presence of polyethylene glycol 6000 since, in this case, the side by side association of actin filaments does not depend on the accessibility of binding sites nor on the formation of chemical bonds.Key words: chemically modified actin, N-ethylmaleimide, pyrene-IA, Cys-374, actin bundles, α-actinin.

Chemical modification of the dihydropyridines binding sites by lysine reagent, pyridoxal 5′-phosphate

1998 ◽  
Vol 32 (4) ◽  
pp. 361-364 ◽  
Author(s):  
Barbara Costa ◽  
Laura Giusti ◽  
Claudia Martini ◽  
Antonio Lucacchini
Keyword(s):  
Chemical Modification ◽  
Binding Sites

TETRAETHYLAMMONIUM-INDUCED CONTRACTIONS OF FROG'S SKELETAL MUSCLE: III. MECHANISM OF ACTION BY CALCIUM RELEASE

1967 ◽  
Vol 45 (5) ◽  
pp. 845-855 ◽  
Author(s):  
G. Beaulieu ◽  
G. B. Frank
Keyword(s):  
Skeletal Muscle ◽  
Mechanism Of Action ◽  
Binding Sites ◽  
Neuromuscular Transmission ◽  
Calcium Concentration ◽  
Calcium Release ◽  
Sartorius Muscle ◽  
Free Solution ◽  
Muscle Twitching ◽  
Solution Bathing

The effects of changes in the extracellular calcium concentration on the muscle 'twitching' response induced by tetraethylammonium of the frog's sartorius muscle were investigated. Decreasing the calcium concentration of a solution bathing the muscle increased the sensitivity of the muscle to TEA stimulation. However, with a sufficient calcium reduction (to 0.108 mM in most preparations) the muscles became completely insensitive to TEA stimulation. In contrast, calcium reduction resulted only in an increased muscle sensitivity to carbachol stimulation. Increasing the calcium concentration greatly decreased TEA sensitivity, and at 2.16 mM calcium a TEA-induced muscle 'twitching' response no longer could be produced. At this calcium concentration carbachol sensitivity was reduced but not eliminated and neuromuscular transmission was essentially unmodified. In studies with the toe muscle, it was found that TEA could restore the potassium-induced contracture that had been eliminated by soaking the muscle in a calcium-free solution. This effect of TEA was dependent upon the presence of a store of bound calcium in the muscle. These results are consistent with the hypothesis that TEA acts by releasing calcium from binding sites on the nerve endings, leading to an increased excitability and instability of these structures and resulting in the muscle twitching response. Other effects of TEA similar to those of increases in calcium are due to an increased level of ionized calcium at nerve and muscle membranes which also results from the release by TEA of calcium from membrane sites.

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