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As demonstrated by a simple procedure based on indirect immunoprecipitation, proteins retained on heparin- Sepharose 4B from postrnitochondrial supernatants of rat liver and Zajdela hepatoma catalyse the translation of rabbit serum albumin rnRNA in the presence of ribosomal subunits from rather, Zajdela hepatoma or rabbit ceticulocytes. The albumin synthesis shows an optimum at 1.5 mM MgCI2 and 25 mM KCl and requires ATP and GTP. It is significantly stimulated by tRNA and proceeds for more than 2 h. suggesting a high rate of reini- tiation. At the optimum ribosomes : rnRNA ratio of 13: 1, the immunoprecipitable radioactivity exceeds 15 - 20-times the blank values. Fluorography of polyacrylamide slabs after electrophoresis of immunoprecipitates revealed the presence of only complete full size serum albumin without any smaller peptides resulting from premature terminations of polypeptide chains, demonstrating faithful translation. In stained gels only, both heavy and light chains of immunoglobulin G were found, indicating that the assay procedure is highly specific and reliable. The fractionated heterologous protein-synthesizing system described in this paper may be generally useful for studies on the synthesis of specific proteins and factors affecting their rates since, unlike comparable translation assays. a precise calculation of the balance of newly synthesized proteins is possible. [ABSTRACT FROM AUTHOR]

From the tryptic hydrolyzate of pig immunoglobulin &kappa-chains 6 cystine-containing fragments were isolated. Amino acids analysis showed that they contained 37-70 amino acid residues and were of a variable nature. There exists a linear relationship between the specific electrical charge of the fragment and the ionic strength of the buffer by which the fragment is eluted from a column of QAE-Sephadex. Fragments, the disulfide bond of which was split by oxidative sulfitolysis, were split by thermolysin and the hydrolyzates were compared by the method of peptide maps. All the maps of fragments tested contained the peptide Ile-ThrSerCysSSO3-Arg (where CysSSO3 = S-sulfo-cysteine) which represents the vicinity of the half-cystine 24 of pig κ-chains, as shown by us previously. The nature of the peptide maps indicates that the individual fragments originate in the same section of the primary structure of the N-terminal half of the κ-chains. Each of the isolated fragments was a mixture of variants with an identical specific charge but with some amino acid replacements. [ABSTRACT FROM AUTHOR]

The ℵ-chains were prepared by chromatography and rechromatography of pig S-sulfoimmunoglobulin on Sephadex G-100 and SE-Sephadex, and characterized by starch-gel electrophoresis, amino acid analysis, molecular weight (25 000 ± 2500) and N-terminal amino add (alanine). From the tryptic digest of the ℵ-chains, the N-terminal tetracosapeptide was isolated and its amino acid sequence determined as Multiples equation(s) cannot be represented by ASCII text. These results provide evidence of the similarity between pig immunoglobulin ℵ-chains and the human and mouse type K Bence-Jones proteins. [ABSTRACT FROM AUTHOR]