Comparison of turnover of several myofibrillar proteins and critical evaluation of double isotope method. [Tritium, /sup 14/C tracer techniques]
The turnover of several myofibrillar proteins in the rat myocardium, namely, myosin heavy chain, light chains, actin, tropomyosin, and ..cap alpha..-actinin, was compared by two methods: the double isotope technique and determination of the specific radioactivity of leucine in electrophoretically separated proteins. The sensitivity of the double isotope method was evaluated by computer analysis of the precursor-product relationship. On the basis of this analysis, we selected experimental conditions whereby maximum discrimination between protein turnover rates could be obtained. In addition, experimentally derived double isotope ratios were converted into half-lives by means of a computer-constructed curve. The turnover rates of individual myofibrillar proteins were related as follows: myosin heavy chain = ..cap alpha..-actinin = tropomyosin>actin>light chain 1 = light chain 2. A similar relationship was obtained when the rate of leucine incorporation into individual myofibrillar proteins was measured. The ratio of light chain 1 and light chain 2 specific radioactivity to that of myosin heavy chain changed with time, however. The ratios were light chain 1/heavy chain = 0.43, light chain 2/heavy chain = 0.38 10 min after administration of label. Four days later, the ratios were 0.71 and 0.77, respectively. The convergence of the specific radioactivities of heavy and light chains of myosin with time is consistent with the existence of a macromolecular precursor of light chains that has not yet been assembled into a complete myosin molecule.
- Research Organization:
- Univ. of Chicago
- OSTI ID:
- 7214525
- Journal Information:
- J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 252:10; ISSN JBCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
550500 -- Metabolism
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMISTRY
BODY
CARBON 14
CARBON ISOTOPES
CARBOXYLIC ACIDS
CARDIOVASCULAR SYSTEM
CHEMISTRY
COMPUTERS
DOUBLE LABELLING
ELECTROPHORESIS
EVEN-EVEN NUCLEI
GLOBULINS
HEART
HYDROGEN ISOTOPES
ISOTOPES
LABELLING
LEUCINE
LIGHT NUCLEI
MAMMALS
METABOLISM
MUSCLES
MYOCARDIUM
MYOSIN
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RADIOISOTOPES
RATS
RODENTS
TRITIUM
VERTEBRATES
YEARS LIVING RADIOISOTOPES