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Observations on an ATP-Sensitive Protein System from the Plasmodia of a Myxomycete

Ts'o, Paul O. P. and Bonner, James and Eggman, Luther and Vinograd, Jerome (1956) Observations on an ATP-Sensitive Protein System from the Plasmodia of a Myxomycete. Journal of General Physiology, 39 (3). pp. 325-347. ISSN 0022-1295. PMCID PMC2147543. doi:10.1085/jgp.39.3.325.

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1. Extracts of the plasmodia of the myxomycete, Physarum polycephalum, exhibit reversible decreases in viscosity in response to the addition of ATP under appropriate conditions. The protoplasm material prepared by extraction with KCl solution can apparently exist in either a high or a low viscosity state. As prepared, it is in the low viscosity condition. Rapid and extensive increases in viscosity of the extract are brought about by addition of AMP, inorganic phosphate, or, under certain conditions, of ATP. Only after the high viscosity state has been attained does addition of appropriate quantities of ATP cause a reversible decrease in viscosity. 2. The active principle of crude plasmodial extracts may be concentrated by fractional precipitation with ammonium sulfate and is found in the fraction precipitated between 30 and 40 per cent saturation. This material possesses a higher viscosity than does the original crude extract and is apparently in the high viscosity state since the addition of ATP causes an immediate reversible decrease in viscosity. 3. The ATP-sensitive fraction of myxomycete plasmodia possesses a viscosity which is dependent upon its previous thermal treatment. Extracts incubated at 0° for a period of a few hours increase greatly in viscosity when they are returned to 24.5°. This increased viscosity is structural in nature, is destroyed by mechanical agitation of the solution, and may be reversibly destroyed by addition of ATP. 4. It is suggested that the ATP-responsive protein of myxomycete plasmodia may be related to sol-gel transformations which have been observed in intact plasmodia and may participate in the protoplasmic streaming of the intact organism. This suggestion is based upon the following facts: (a) the protoplasmic streaming of myxomycete plasmodia is increased by microinjection of ATP; (b) the gel portion of the cytoplasm at the site of the microinjection of ATP is extensively converted to the sol state. The changes in structure of the intact cytoplasm are thus similar in nature to the changes exhibited in response to ATP by the purified ATP-sensitive protein. 5. The ATP-sensitive protein of myxomycete plasmodia appears to undergo reversible aggregation to form a high viscosity state. The function of ATP is to break down the aggregates thus formed. Since a specific ATPase activity is associated with the purified material, added ATP is gradually destroyed and recovery of viscosity attends the spontaneous reconstitution of aggregates.

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Additional Information:© 1956 Rockefeller University Press. After six months the work becomes available to the public to copy, distribute, or display under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported license. Received for publication, June 13, 1955. Report of work supported in part by a grant from the National Institutes of Health, United States Public Health Service.
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Issue or Number:3
PubMed Central ID:PMC2147543
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Official Citation:OBSERVATIONS ON AN ATP-SENSITIVE PROTEIN SYSTEM FROM THE PLASMODIA OF A MYXOMYCETE Paul O. P. Ts'o, James Bonner, Luther Eggman, Jerome Vinograd The Journal of General Physiology Jan 1956, 39 (3) 325-347; DOI: 10.1085/jgp.39.3.325
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49958
Deposited By: Tony Diaz
Deposited On:23 Sep 2014 22:18
Last Modified:10 Nov 2021 18:50

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