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Biomedical subjects

P Dreizen

Publications and source records attributed to P Dreizen.

18 recordsLinked to original sources
PubMed1984

Structural studies of glycerinated skeletal muscle. I. A-band length and cross-bridge period in ATP-contracted fibers.

An electron microscope study is reported of structural changes during ATP-induced contraction of glycerinated rabbit psoas. In the absence of ATP, A-band length is constant at sarcomere lengths above 1.9 micron, with average length of 1.54 mu. In ATP-treated fibers, A-band length is also constant at sarcomere lengths above 2.0 microns, but the apparent length of A-band decreases to approximately 1.3 micron, as sarcomere length decreases from 1.9 micron to 1.5 mu. The occurrence of short A-bands cannot be attributed to crumpling of thick filaments against Z-lines, since I-bands remain patent; nor to the presence of heterogeneous filaments, since resting muscle does not show comparable heterogeneity, nor to compressive artifacts, which are minor when knife edge is oriented parallel with fiber axis during microtomy . The decrease of A-band length appears related, at least in part, to disarray of terminal cross-bridges as the thick filaments encroach upon the N-line, a structure which becomes evident within the I-band during contraction of glycerinated fibers. In preliminary studies, optical transforms of A-bands from individual sarcomeres reveal a characteristic myosin layer-line pattern as low as 1.5 micron sarcomere length. A cross-bridge repeat of 143 A is obtained for sarcomeres above 1.6 micron length; however, an appreciable proportion of sarcomeres in the range from 1.5 micron to 1.9 mu length generate meridional reflections less than 143 A, and as low as 130 A.

Adenosine Triphosphate↗
PubMed1979

Structural studies of natural actomyosin from thermally acclimated frogs.

Natural actomyosin was isolated from skeletal muscle of frogs (Rana catesbeiana) acclimated at 25 degrees C and 5 degrees C. It was found that preparations isolated from warm-acclimated frogs may display considerable degradation of myosin heavy chains as compared with preparations isolated from cold-acclimated frogs. However, degradation may be minimized by inclusion of protease inhibitors during purification, indicating enhanced protease activity in preparations of natural actomyosin from warm-acclimated frogs. When purified in the presence of protease inhibitors, natural actomyosin from both warm-acclimated and cold-acclimated frogs exhibits comparable subunit composition of SDS-gel electrophoresis. The overall gel pattern is similar to that obtained from rabbit natural actomyosin except that in the frog, troponin-T and troponin-C appear to co-migrate with tropomyosin and myosin light chain 2, respectively.

Acclimatization↗
PubMed1978

Structural properties of frog muscle myosin.

Frog myosin is a labile molecule, undergoing irreversible aggregation and rapid loss of ATPase; however, a procedure is described which provides highly purified myosin, with stable solubility and enzymatic properties, from skeletal muscle of Rana catesbeiana. Frog myosin contains heavy chains and light chains 1, 2, and 3. Light chain 3 is present in excess over light chain 1, and light chain 2 may occur as either, or both, of 2 closely migrating bands. On two-dimensional electrophoresis, light chain 1 generates an isoelectric component with pK 5.60; light chain 2 generates a complex pattern with 3 or 4 major components; and light chain 3 generates 2 major components with pK 5.00 and 4.92. The same subunit composition is obtained for frogs acclimated at 25 and 5 degrees C; however, proteolytic artifacts may occur in myosin preparations purified in the absence of protease inhibitors, especially in warm-acclimated frogs.

Acclimatization↗
PubMed1978

Canine cardiac myosin with special referrence to pressure overload cardiac hypertrophy. I. Subunit composition.

In studies of myosin from left and right ventricles of normal hearts and hypertrophic hearts at 5 weeks and 13 weeks after aortic banding, polyacrylamide gel electrophoresis shows intermediate molecular weight components which derive from heavy chains fragmented in the presence of dodecyl sulfate. The proportion of degraded heavy chains is greater in myosin from hypertrophic hearts than normal hearts, with comparable degradation in left and right ventricle myosin. The observed fragmentation of myosin results from proteolysis due to contaminant proteases or a thermally activated, heat-stable nonenzymatic process, or both. The susceptibility of heavy chains to crude myofibrillar proteases differs in normal and hypertrophic cardiac myosin; however, the kinetics of tryptic digestion are identical for both myosins. With precautions to minimize proteolytic artifacts on dodecyl sulfate-polyacrylamide gel electrophoresis, preparations of myosin from left and right ventricles of normal and hypertrophic hearts exhibit comparable subunit composition, with approximately molar ratios of heavy chains, light chain L1, and light chain L2. Comparable stoichiometry for the light chain fraction is determined by high speed sedimentation equilibrium at pH 11 and direct fractionation of the different cardiac myosins. We do not confirm reports (e.g. Wikman-Coffelt, J., Fenner, C., Smith, A., and Mason, D. T. (1975) J. Biol. Chem. 250, 1257-1262) of different proportions of light chains in left and right ventricle myosin of normal and hypertrophic canine hearts. The light chains display microheterogeneity, with L1 generating two isoelectric variants and L2 generating two major and two minor variants, but identical mobilities and isoelectric values are obtained in the different myosin preparations.

Animals↗
PubMed1978

A new analytical procedure for two-dimensional electrophoresis of cellular proteins: comparison of protein compositions of parent strain and a K+-accumulation mutant of E. coli.

An improved two-dimensional analytical electrophoretic technique fractionates according to molecular weight in the presence of dedecyl sulfate in the first dimension, then fractionates according to isoelectric point in a perpendicular dimension. Electrofocusing in the second dimension achieves nearly complete removal of most protein components while providing true estimates of their isoelectric points. Because not all proteins penetrate isoelectric focusing gels, some proteins may go unrecognized using conventional two-dimensional systems where isoelectric focusing precedes electrophoresis. However, such components do enter dodecyl sulfate gels; hence the presence and molecular weight of those components can be established by the new procedure. A concurrent finding was that, in general, penetration of isoelectric focusing gels by discrete protein subunits dissolved in 9 M urea is an all-or-none phenomenon depending on the solubility of the specific subunit. The procedure was applied to comparison of the protein compositions of a parental strain (CBH) of Escherichia coli and a derived mutant strain (RD-2) deficient in ability to accumulate K+. The strains showed similar two-dimensional patterns except for one discrete isoelectric component absent in the parent strain but present in the mutant.

Bacterial Proteins↗
PubMed1967

Subunits and their interactions.

There is fairly general agreement that myosin isolated from rabbit skeletal muscle has a molecular weight of about 500,000. The higher values that have been reported apparently reflect protein aggregation related to the method of preparation. On the basis of present evidence, the myosin molecule has an elongate helical core of two f subunits (average weight about 215,000) that extend into a globular head region containing three g subunits (average weight about 20,000). Myosin may be dissociated into subunits by a number of methods. In 5 M guanidine, the myosin molecule is dissociated into f and g subunits, while at pH above 10, the g subunits are dissociated from the intact fibrous core of myosin. The dissociation of g subunits at pH 10 is accompanied by the loss of both ATPase activity and actin-binding capacity; however, the exact biological significance of the g subunits is presently uncertain. In preliminary studies, the f subunits appear to contain the sulfhydryl residues currently implicated in myosin ATPase, and there is some indication of allosteric regulation of enzymic activity.

Adenosine Triphosphatases↗