Prothymosin .alpha.: A Biologically Active Protein with Random Coil Conformation

Gast, Klaus; Damaschun, Hilde; Eckert, K; Schulze‐Forster, Kai; Maurer, H. R.; Müller-Frohne, Marlies; Zirwer, Dietrich; Czarnecki, J; Damaschun, G.

doi:10.1021/bi00040a037

Cited by 200 publications

(171 citation statements)

References 46 publications

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“…On the one hand, free ProTa failed to acquire structured conformation even at 200 mm Zn 21 , as judged by our differential scanning calorimetry measurements (V. Orlov and A. G. Evstafieva, unpublished results). This observation was in accord with the data of Gast et al [8], which proved that the random coil conformation of free ProTa is preserved in the presence of millimolar concentrations of Mg 21 , Ca 21 , and Zn 21 ions. However, recent data [35] suggest that, at 12 mm Zn 21 , this cation can induce some rearrangement of the ProTa structure.…”

Section: Discussionsupporting

confidence: 92%

“…The peculiar amino-acid composition of ProTa results in its exceptional acidity (pI < 3.5) and hydrophilicity, manifested by the unique ability of the protein to partition into the aqueous phase on phenol extraction [5,6]. Attempts to identify the elements of regular structure in ProTa using various approaches were unsuccessful and led to the conclusion that ProTa possesses a rare random coil conformation [7,8], at least under physiological conditions. ProTa was found in virtually all mammalian tissues studied, with the highest content in the thymus [9].…”

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confidence: 99%

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Divalent metal cation binding properties of human prothymosin α

Chichkova

Evstafieva

Lyakhov

et al. 2000

European Journal of Biochemistry

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The divalent cation binding properties of human prothymosin a, an abundant nuclear protein involved in cell proliferation, were evaluated. By using prothymosin a retardation on a weak cation chelating resin charged with various divalent cations, specific binding of Zn 21 ions by prothymosin a was observed. This finding was further confirmed by the equilibrium dialysis analysis which demonstrated that, within the micromolar range of Zn 21 concentrations, prothymosin a could bind up to three zinc ions in the presence of 100 mm NaCl and up to 13 zinc ions in the absence of NaCl. Equilibrium dialysis analysis also revealed that prothymosin a could bind Ca 21 , although the parameters of Ca 21 binding by prothymosin a were less pronounced than those of Zn 21 binding in terms of the number of metal ions bound, the K D values, and the resistance of the bound metal ions to 100 mm NaCl. The effects of Zn 21 and Ca 21 on the interaction of prothymosin a with its putative partners, Rev of HIV type 1 and histone H1, were examined. We demonstrated that Rev binds prothymosin a, and that prothymosin a binding to Rev but not to histone H1 was significantly enhanced in the presence of zinc and calcium ions. Our data suggest that the modes of prothymosin a interaction with Rev and histone H1 are distinct and that the observed zinc and calcium-binding properties of prothymosin a might be functionally relevant.

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Section: Discussionsupporting

confidence: 92%

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confidence: 99%

Divalent metal cation binding properties of human prothymosin α

Chichkova

Evstafieva

Lyakhov

et al. 2000

European Journal of Biochemistry

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“…1) Mutant human prothymosin ␣ molecules lacking Ser 1 , the sole confirmed repository of phosphate, continued to become phosphorylated. Because prothymosin ␣ in solution is unfolded (38), the data cannot readily be understood by invoking cryptic sites of phosphorylation in mutants. Rather, our data fit a model in which both mutant and wild type prothymosin ␣ molecules initially acquire phosphate at the same site and subsequently transfer it to a stable location.…”

Section: Discussionmentioning

confidence: 99%

Prothymosin α in Vivo Contains Phosphorylated Glutamic Acid Residues

Trumbore

Wang

Enkemann

et al. 1997

Journal of Biological Chemistry

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2) Immediately upon cell lysis, the pH stability curves of metabolically labeled native [ 32 P]prothymosin ␣ or a [ 32 P]histidine-tagged variant resembled the pH stability curve of acetyl phosphate. 3) After a brief incubation at pH 7, these curves changed from a pattern diagnostic for an acyl phosphate to that characteristic of a serine or threonine phosphate, an observation consistent with transfer of phosphate in vitro. Our data indicate that most of prothymosin ␣'s phosphates are subject instantaneously to hydrolysis, based on the observation that greater than 90% of the phosphate initially found at pH 7 disappeared at the extremes of pH. Rapid loss of phosphate was not affected by the presence of phosphatase inhibitors including 50 mM sodium fluoride, 1 mM okadaic acid, and 0.5 mM calyculin A. The amount of phosphate missing could not be ascertained, but the trifling amount recovered on Ser or Thr depended heavily on conditions favoring the transient survival of labile phosphate. Further analysis using COS cells lysed in the presence of sodium borohydride showed that: 1) phosphate recovered on prothymosin ␣ decreased 8-fold when lysates were treated with borohydride; 2) the reagent caused 4 -8 glutamic acid residues/molecule to vanish; 3) using [ 3 H]NaBH 4 , label was introduced into proline, a product derived from reductive cleavage of phosphoglutamate; and 4) [ 3 H]proline was localized almost exclusively to a peptide with pronounced homology to the histone binding site of nucleoplasmin, a chromatin remodeling protein found in Xenopus laevis. Our data demonstrate that prothymosin ␣ is energy-rich by virtue of stoichiometric amounts of glutamyl phosphate.Prothymosin ␣ is a highly unusual protein with an unfortunate name. The protein is neither a precursor for processed polypeptides nor specifically associated with the thymus nor a member of a family with ␤ or ␥ homologues (1-3). Instead, it is probably the most acidic naturally occurring polypeptide in the eukaryotic world, with 54 carboxyl groups in 109 amino acids, resulting in an isoelectric point at or below pH 3.5 (1, 2, 4). The mRNA for prothymosin ␣ is distributed ubiquitously among mammalian nucleated cells and tissues (1). The protein possesses a potent nuclear localization signal and is present in amounts equivalent to those of histone H1 (5, 6). Because the amount of prothymosin ␣ mRNA (and presumably protein) found in a cell is directly proportional to cell growth, the protein is believed to play a role in cell proliferation (1). This idea was reinforced by the observation that synchronized human myeloma cells, in the presence of antisense oligodeoxyribonucleotides directed at prothymosin ␣ mRNA, were unable to divide while detectable amounts of the antisense oligonucleotides remained inside the cell (7). There are now many examples of a link between prothymosin ␣ and growth in systems as diverse as developing mouse embryos (8); normal, mitogenstimulated, and malignant lymphocytes (9, 10); and regenerating liver (10). There are also positive ...

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“…According to the different isoelectric points, thymosins are classified into three categories: α-thymosins (pH < 5.0), β-thymosins (5.0 < pH < 7.0) and γ-thymosins (pH > 7.0) (Hannappel and Huff, 2003). Prothymosin alpha (ProTα), the precursor of α-thymosins, is a small acidic nuclear protein, containing 109-113 amino acids depending on the species, consisting mainly of aspartic and glutamic acid residues (more than 50%) with few hydrophobic amino acids and without any aromatic or sulfur amino acids (Gast et al, 1995). Beta thymosins (Tβs) are a family of highly conserved polar 5-kDa polypeptides consisting of 40-44 amino acid residues.…”

Section: Introductionmentioning

confidence: 99%