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Prothymosin alpha is phosphorylated by casein kinase-2.
M G Barcia1, J M Castro, C D Jullien
1Departamento de Bioquímica e Bioloxía Molecular, Facultade de Bioloxía, Universidade de Santiago, Galicia, Spain.
FEBS Letters
|November 9, 1992
Summary
Prothymosin alpha (ProT alpha), a protein involved in cell proliferation, is phosphorylated by casein kinase-2 (CK-2) in vitro and in vivo. This phosphorylation occurs at specific threonine residues, suggesting CK-2
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Prothymosin alpha (ProT alpha) is an acidic polypeptide implicated in nuclear functions and cell proliferation.
- Its amino acid sequence contains potential phosphorylation sites for casein kinase-2 (CK-2).
Purpose of the Study:
- To investigate the phosphorylation of ProT alpha by CK-2.
- To identify the specific sites and conditions of ProT alpha phosphorylation in vitro and in vivo.
Main Methods:
- In vitro phosphorylation assays using purified ProT alpha and CK-2.
- Analysis of ProT alpha amino acid sequence for potential phosphorylation sites.
- In vivo phosphorylation studies using cultured splenic lymphocytes.
Main Results:
- ProT alpha was phosphorylated by CK-2 in vitro at Ser and Thr residues within the first 14 amino acids.
- Thymosin alpha 1 (T alpha 1), a fragment of ProT alpha, also phosphorylated by CK-2 at similar sites.
- In cultured lymphocytes, ProT alpha phosphorylation occurred at Thr residues at positions 7, 12, and/or 13.
Conclusions:
- CK-2, or a kinase with similar specificity, phosphorylates ProT alpha in vivo.
- Phosphorylation sites are primarily located within the N-terminal region of ProT alpha.