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      Construction, Expression, and Characterization of Thymosin Alpha 1 Tandem Repeats in Escherichia coli

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          Abstract

          Thymosin alpha 1 (T α 1), which is composed of 28 amino acids, has been commercialized worldwide for its immune-modulatory and antitumor effects. T α 1 can stimulate T cell proliferation and differentiation from bone marrow stem cells, augment cell-mediated immune responses, and regulate homeostasis of immune system. In this study, we developed a novel strategy to produce T α 1 concatemer (T α 1 ) in Escherichia coli and compared its activity with chemically synthesized T α 1. Results showed that T α 1 can more effectively stimulate T cell proliferation and significantly upregulate IL-2 receptor expression. We concluded that the expression system for T α 1 concatemer was constructed successfully, which could serve as an efficient tool for the production of large quantities of the active protein.

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          Thymosin alpha1: isolation and sequence analysis of an immunologically active thymic polypeptide.

          The amino acid sequence of a biologically active polypeptide isolated from calf thymus, termed thymosin alpha1, has been determined. Thymosin alpha1 is a heat stable, highly acidic molecule composed of 28 amino acid residues. This peptide is one of several present in thymosin fraction 5 that may participate in the regulation, differentiation and function of thymus-dependent lymphocytes (T cells). A nomenclature for the family of polypeptides present in thymosin fraction 5 is suggested.
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            Tandem amino acid repeats from Trypanosoma cruzi shed antigens increase the half-life of proteins in blood.

            Proteins containing amino acid repeats are widespread among protozoan parasites. It has been suggested that these repetitive structures act as immunomodulators, but other functional aspects may be of primary importance. We have recently suggested that tandem repeats present in Trypanosoma cruzi trans-sialidase stabilize the catalytic activity in blood. Because the parasite releases trans-sialidase, this delayed clearance of the enzyme might have implications in vivo. In the present work, the ability of repetitive units from different T. cruzi molecules in stabilizing trans-sialidase activity in blood was evaluated. It is shown that repeats present on T. cruzi shed proteins (antigens 13 and Shed-Acute-Phase-Antigen [SAPA]) increase trans-sialidase half-life in blood from 7 to almost 35 hours. Conversely, those repeats present in intracellular T. cruzi proteins only increase the enzyme half-life in blood up to 15 hours. Despite these results, comparative analysis of structural and catalytic properties of both groups of chimeric enzymes show no substantial differences. Interestingly, antigens 13 and SAPA also increase the persistence in blood of chimeric glutathione S-transferases, thus suggesting that this effect is inherent to these repeats and independent of the carrier protein. Although the molecular basis of this phenomenon is still uncertain, its biotechnological potential can be envisaged.
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              The chemistry and biology of thymosin. II. Amino acid sequence analysis of thymosin alpha1 and polypeptide beta1.

              The amino acid sequences of two polypeptide components of thymosin Fraction 5 termed thymosin alpha1 and polypeptide beta1 have been established. The sequences were determined by automatic Edman degradation of the intact molecules as well as by manual sequence analysis of the enzymatic cleavage products. Thymosin alpha1, an immunologically active polypeptide, is highly acidic with an isoelectric point of 4.2. This molecule is composed of 28 amino acid residues with acetylserine as the NH2 terminus. A chemically synthesized molecule of thymosin alpha1 has been found to be as active as the natural molecule in our bioassay systems. Polypeptide beta1 is a molecule consisting of 74 amino acid residues and has an isoelectric point of 6.7. This peptide is not biologically active in our assay systems, suggesting that it is not involved in thymic hormone action. The sequence of beta1 was found to be identical with ubiquitin and a portion of protein A24, a nuclear chromosomal protein. The relationships among these proteins are discussed.
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                Author and article information

                Journal
                Biomed Res Int
                Biomed Res Int
                BMRI
                BioMed Research International
                Hindawi Publishing Corporation
                2314-6133
                2314-6141
                2013
                28 February 2013
                : 2013
                : 720285
                Affiliations
                State Key Laboratory of Cancer Biology, Department of Biopharmaceutics, School of Pharmacy, Fourth Military Medical University, Xi'an 710032, China
                Author notes

                Academic Editor: Fabio Ferreira Perazzo

                Article
                10.1155/2013/720285
                3600210
                23555093
                0ad6c78f-2498-4a9f-bf6a-88482b0283b9
                Copyright © 2013 Xiao-Chang Xue et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 11 June 2012
                : 26 November 2012
                : 26 November 2012
                Categories
                Research Article

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