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Biomedical subjects

G Offer

Publications and source records attributed to G Offer.

At least 37 records · Page 2Linked to original sources
PubMed1981

Structure of filamin and the F-actin-heavy merofilamin complex.

Rotary-shadowed filamin molecules appear as long, highly flexible rods curved into a variety of configurations. The particles observed were 2.7 nm wide but had contour lengths of either 98 nm or 193 nm. The longer particles are probably end-to-end dimers of the shorter but it is not clear how many polypeptide chains these particles contain. Heavy merofilamin, obtained by digestion of filamin with a calcium-activated protease from muscle, has been used to investigate where filamin binds on the actin filaments. Negatively stained filaments of actin plus heavy merofilamin resemble those of pure actin; occasionally rod-shaped material sticking out from the filament is observed suggesting that the elongated shape of filamin is maintained after digestion. Optical diffraction patterns of electron micrographs of paracrystals of actin plus heavy merofilamin indicate that the helical symmetry of the actin filament is unchanged, but the observed interfilament spacing is larger than in F-actin paracrystals. Increased intensity of the second layer-line reflection is observed, suggesting that additional material is lying along the grooves of the actin helix. The elongated shape of filamin and its ability to bind to F-actin in a way similar to tropomyosin suggest a possible role for this protein in regulating the organization and aggregation of actin filaments.

Actins↗
PubMed1980

Investigation, by cross-linking, of conformational changes in F-actin during its interactions with myosin.

The hypothesis that the subunits of F-actin rotate during interactin with myosin and ATP has been tested by using the specific cross-linking reagent p-phenylene-N,N'-bis(maleimide) (PM). The insertion of cross-links between F-actin subunits does not change the ability of the F-actin to activate the ATPase of either myosin subfragment-1 (S-1) or heavy meormyosin, and its ability to superprecipitate with myosin is unimpaired. We conclude that large-scale rotations of actin subunits are not required for activity. The cross-linking of F-actin by PM is, however, inhibited in a noncooperative fashion by S-1 binding, suggesting that a small local change in actin structure may accompany the binding of S-1 or that S-1 sterically blocks the cross-linking by binding near the contact region between actin subunits.

Actins↗
PubMed1978

p-NN'-phenylenebismaleimide, a specific cross-linking agent for F-actin.

Covalent cross-links can be inserted between the subunits of F-actin by using p-NN'-phenylenebismaleimide. Cross-linking reaches its maximum value when one molecule of reagent has reacted with each actin subunit. p-NN'-Phenylenebismaleimide reacts initially with a cysteine residue on one subunit, the slower cross-linking reaction involving a lysine residue on a neighbouring subunit. Hydrolysis of the actin-bound reagent limits the extent of cross-linking. Quantitative analysis of the amounts of cross-linked oligomers seen on polyacrylamide gels containing sodium dodecyl sulphate suggests that neither the binding of the reagent to actin nor the formation of cross-links introduces strain into the structure. The cross-links do not join together different F-actin filaments, and evidence is presented that suggests that the cross-links join subunits of the same long-pitched helix.

Actins↗
PubMed1978

The interaction of C-protein with heavy meromyosin and subfragment-2.

C-protein has previously been shown to bind to the light-meromyosin region of the myosin tail. Examination of mixtures of C-protein with heavy meromyosin or subfragment-2 or subfragment-1 in the analytical ultracentrifuge shows that there is also a binding site for C-protein in the subfragment-2 region of the tail.

Binding Sites↗
PubMed1978

Can a myosin molecule bind to two actin filaments?

It is suggested that in striated muscles the two heads of one myosin molecule are able to interact with different actin filaments. This would provide a simple explanation for the appearance and arrangement of cross-bridges in insect flight muscle in rigor.

Actins↗
PubMed1977

[Hashimoto's thyroiditis. Clinical contribution].

--After a brief account of anatomical and clinical findings of Hashimoto's thyroiditis, 8 cases, personally observed, are presented. The various aspects of this disease and in particular the most recent diagnostic methods are examined and therapeutical possibilities, from the medical and surgical standpoint, are discussed.

Adolescent↗