Abstract
The A filament of the striated muscle sarcomere is an ordered aggregate of one or a few species of proteins. Ordering of these filaments into a parallel array is the basis of birefringence in the A region, and loss of birefringence is therefore a measure of decreased order. Heating caused a large decrease in the birefringence of glycerinated rabbit psoas muscle fibers over a narrow temperature range (∼3°C) and a large decrease in both the birefringence and optical density of the A region of Drosophila melanogaster fibrils. These changes were interpreted as a loss of A filament structure and were used to define a transition temperature (Ttr) as a measure of the stability of the A region. Since the transition temperature was sensitive to pH, ionic strength, and urea, solvent conditions which often affect protein structure, it is an experimentally useful indicator for factors affecting the structure of the A filament. Fibers from glycerinated frog muscle were less stable over a wide pH range than fibers from glycerinated rabbit muscle, a fact which demonstrates a species difference in structure. Glycerinated rabbit fibrils heated to 70°C shortened to about 40% of their initial length. The extent of shortening was not correlated with the loss of birefringence, and phase-contrast microscopy showed that this shortening occurred in the I region as well as in the A region. This response may be useful for studying the I filament and actin in much the same way that the decrease in birefringence was used for studying the A filament and myosin. The observations presented show that some properties of muscle proteins can be studied essentially in situ without the necessity of first dispersing the structure in solutions of high or low ionic strength.
Full Text
The Full Text of this article is available as a PDF (983.5 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- ARONSON J. The elongation of myofibrils from the indirect flight muscle of Drosophila. J Cell Biol. 1962 Apr;13:33–41. doi: 10.1083/jcb.13.1.33. [DOI] [PMC free article] [PubMed] [Google Scholar]
- BENESCH R., BENESCH R. E. Determination of--SH groups in proteins. Methods Biochem Anal. 1962;10:43–70. doi: 10.1002/9780470110270.ch2. [DOI] [PubMed] [Google Scholar]
- HANSON J., HUXLEY H. E. Quantitative studies on the structure of cross-striated myofibrils. II. Investigations by biochemical techniques. Biochim Biophys Acta. 1957 Feb;23(2):250–260. doi: 10.1016/0006-3002(57)90326-8. [DOI] [PubMed] [Google Scholar]
- HOEVE C. A., WILLIS Y. A. Elasticity of the fibrous muscle proteins. Biochemistry. 1963 Mar-Apr;2:279–282. doi: 10.1021/bi00902a013. [DOI] [PubMed] [Google Scholar]
- HOTTA K., KOJIMA S. STUDIES ON STRUCTURE AND ENZYMATIC ACTIVITY OF MYOSIN. RELATIONSHIP BETWEEN CONFORMATIONS AND ADENOSINE TRIPHOSPHATASE ACTIVITY OF MYOSIN AND H-MEROMYOSIN IN UREA. Biochemistry. 1964 Oct;3:1431–1436. doi: 10.1021/bi00898a007. [DOI] [PubMed] [Google Scholar]
- KAY C. M., BRAHMS J. THE INFLUENCE OF ETHYLENE GLYCOL ON THE ENZYMATIC ADENOSINE TRIPHOSPHATASE ACTIVITY AND MOLECULAR CONFORMATION OF FIBROUS MUSCLE PROTEINS. J Biol Chem. 1963 Sep;238:2945–2949. [PubMed] [Google Scholar]
- LOWEY S., COHEN C. Studies on the structure of myosin. J Mol Biol. 1962 Apr;4:293–308. doi: 10.1016/s0022-2836(62)80007-2. [DOI] [PubMed] [Google Scholar]
- RUDALL K. M. The proteins of the mammalian epidermis. Adv Protein Chem. 1952;7:253–290. doi: 10.1016/s0065-3233(08)60020-0. [DOI] [PubMed] [Google Scholar]
- SZENT-GYORGYI A. G., BORBIRO M. Depolymerization of light meromyosin by urea. Arch Biochem Biophys. 1956 Jan;60(1):180–197. doi: 10.1016/0003-9861(56)90410-6. [DOI] [PubMed] [Google Scholar]
- WEBER H. H., PORTZEHL H. Muscle contraction and fibrous muscle proteins. Adv Protein Chem. 1952;7:161–252. doi: 10.1016/s0065-3233(08)60019-4. [DOI] [PubMed] [Google Scholar]
- Warren J. C., Stowring L., Morales M. F. The effect of structure-disrupting ions on the activity of myosin and other enzymes. J Biol Chem. 1966 Jan 25;241(2):309–316. [PubMed] [Google Scholar]