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Paracrystalline assemblies of light meromyosins with various chain weights.
J Muscle Res Cell Motil 6, 641-58.
Paracrystals formed from well defined insoluble fragments of myosin rod: LMM-A, LMM-B, LMM-C, and LMM-D with apparent chain weights of 78 000, 72 000, 68 000, and 56 000, respectively (Nyitray et al., 1983) were studied in the electron microscope with a negative staining technique. All fragments formed tactoids with 14.3 and 43 nm periodicities as well as aperiodic tactoids and sheets. Tactoids and sheets described earlier with a 43 nm periodicity and a pattern of alternating light bands 10 nm wide and dark bands 33 nm wide were observed in LMM-A preparations only. LMM-B and LMM-C formed tactoids with a 43 nm periodicity but without the diversified band pattern. LMM-D formed sheets and tactoids with a newly observed band pattern of alternating light bands 23 nm wide and dark bands 20 nm wide. This pattern can be explained assuming the length of LMM-D molecules to be 66 nm which is fairly consistent with the chain weight of this fragment. A model for molecular arrangement in this type of paracrystal is presented. The model involves both parallel and antiparallel interactions with a parallel axial displacement of the molecules by 43 nm as suggested by Bennett (1981) for paracrystals formed from LMM molecules 90 nm long. It is deduced from the model that LMM-D is shorter than LMM-A by 15 nm at the NH2-terminal end and by 9 nm at the COOH-terminal end. LMM-D, like the other insoluble fragments of myosin rod, is also able to form square and hexagonal nets with an approximately 40 nm distance between lattice points. The structural features of the nets obtained from LMM-D can be explained assuming the same kinds of molecular interactions within the strands of the net as those in the sheets and tactoids with a 43 nm axial repeat. It is concluded that all insoluble fragments of myosin rod are able to form paracrystalline assemblies involving the same types of parallel and antiparallel interactions.
Naloxone antagonises effect of alpha-gliadin on leucocyte migration in patients with coeliac disease.
Lancet 2, 184-5.
The effect of naloxone on inhibition of leucocyte migration by alpha-gliadin was examined in 24 patients with coeliac disease. In all cases in which alpha-gliadin inhibited leucocyte migration, naloxone blocked this inhibitory effect, which suggests that the effect of gliadin on lymphocytes from patients with coeliac disease may be mediated through opioid-like receptors.
Action of neutral metalloendopeptidase (
Neuropeptides 6, 13-9.
Human beta-endorphin was digested by neutral metalloendopeptidase from rabbit kidney and the products were isolated and identified. Based on the structure and yield of the fragments, the major cleavage sites were identified with the Leu17-Phe18, Gly3-Phe4, Pro13-Leu14 and Ile22-Ile23 peptide bonds of the beta-endorphin structure. The cleavage of the Leu17-Phe18 bond appears to be the rate-limiting step of the enzymic conversion similarly to the previously proposed pathways of beta-endorphin degradation by brain homogenates and synaptic membranes.