TY - JOUR
T1 - Changes in cytoplasmic DNA-binding phosphoproteins during the cell cycle of Physarum polycephalum
AU - Magun, Bruce
N1 - Funding Information:
This work was supported in part by grants from the U.S.P.H.S. (CA-20913).
PY - 1979/4
Y1 - 1979/4
N2 - The cytoplasmic DNA-binding proteins of Physarum polycephalum were examined during two successive cell cycles for alterations in the phosphorylated species. Plasmodia were grown continuously in [3H]leucine and [32P]orthophosphate in order to label proteins with 3H and phosphoproteins additionally with 32P. Cytosol proteins were passed through columns of double-and single-stranded DNA cellulose. Proteins with affinity for DNA-cellulose were eluted with increasing NaCl concentrations and were examined by polyacrylamide gel electrophoresis and gel autoradiography. A general decrease in phosphorus content of approx. 30% was found in both DNA-binding and non-binding proteins during the G2 phase of the cell cycle. When compared among the cytoplasmic DNA-binding proteins this decreased phosphorus content was attributable to the attenuation or disappearance of several phosphorylated DNA-binding proteins. In addition, several differences in the polypeptide profiles of phosphorylated and non-phosphorylated DNA-binding proteins were found at the same point in two successive cell cycles. In general, there was a decreased phosphate content among the DNA-binding proteins during the second successive cell cycle. It is suggested that this decrease is related to a depletion of nutrients, and that the coordinated alterations in the phosphate content of most cytoplasmic DNA-binding proteins is indicative of their functional relatedness.
AB - The cytoplasmic DNA-binding proteins of Physarum polycephalum were examined during two successive cell cycles for alterations in the phosphorylated species. Plasmodia were grown continuously in [3H]leucine and [32P]orthophosphate in order to label proteins with 3H and phosphoproteins additionally with 32P. Cytosol proteins were passed through columns of double-and single-stranded DNA cellulose. Proteins with affinity for DNA-cellulose were eluted with increasing NaCl concentrations and were examined by polyacrylamide gel electrophoresis and gel autoradiography. A general decrease in phosphorus content of approx. 30% was found in both DNA-binding and non-binding proteins during the G2 phase of the cell cycle. When compared among the cytoplasmic DNA-binding proteins this decreased phosphorus content was attributable to the attenuation or disappearance of several phosphorylated DNA-binding proteins. In addition, several differences in the polypeptide profiles of phosphorylated and non-phosphorylated DNA-binding proteins were found at the same point in two successive cell cycles. In general, there was a decreased phosphate content among the DNA-binding proteins during the second successive cell cycle. It is suggested that this decrease is related to a depletion of nutrients, and that the coordinated alterations in the phosphate content of most cytoplasmic DNA-binding proteins is indicative of their functional relatedness.
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U2 - 10.1016/0045-6039(79)90035-6
DO - 10.1016/0045-6039(79)90035-6
M3 - Article
C2 - 466702
AN - SCOPUS:0018362545
SN - 0045-6039
VL - 8
SP - 157
EP - 172
JO - Cell Differentiation
JF - Cell Differentiation
IS - 2
ER -