Saline-soluble Proteins Research Articles

THE INCORPORATION OF [14C]LYSINE INTO THE PROTEIN OF THE GUINEA PIG CENTRAL AUDITORY SYSTEM1

Abstract—The incorporation of [14C]lysine into various brain proteins was studied. The proteins of different areas of the auditory system and cortical subcellular fractions were analysed using a disc electrophoretic technique that allows both protein and radioactivity assays along the gels. The highest level of incorporation was found in the mid brain nuclei, particularly the inferior colliculus, and was lowest in the auditory cortex proteins. This was true for both saline soluble proteins and proteins solubilized by Triton X‐100 treatment. Of the subcellular fractions, the highest level of activity was found in the microsomal fraction. Considerable radioactivity was also found in the proteins isolated from the synaptosome‐rich fraction. Of particular interest in this fraction was a slow migrating protein band which was soluble in Triton X‐100, had a high specific activity, and appeared to be synaptosome specific. These observations are in concurrence with the hypothesis that the nerve ending contains protein synthesizing machinery.

Some aspects of the mechanism of action of 1-propyl-1-nitrosourea

Activation of RNA synthesis with simultaneous suppression of DNA synthesis in experiments with Ehrlich ascites carcinoma and 22 solid hepatoma in mice was observed 20–40 min after administration of 1-propyl-1-nitrosourea (PNU) in a dose of 10 mg/kg. Under these experimental conditions DNA biosynthesis in tumor cells was inhibited earlier than in spleen and in liver cells of tumor-bearing mice and control mice. Inhibition of synthesis of DNA and ribosomal and transfer RNA in the ascites cells, as well as of DNA and total RNA of the liver and spleen of tumor-bearing mice and controls, was observed on increasing the dose PNU to 200 mg/kg. PNU concentration of 10 −4 M was shown to induce RNA synthesis activation in vitro with simultaneous suppression of DNA synthesis in Ehrlich ascites carcinoma and leukemia L1210 cells PNU inhibits synthesis of arginine-rich histone and activates synthesis of lysine-rich histone; synthesis of saline-soluble proteins remains unchanged (at a PNU concentration of 10 −4 M).

Effects of administration of thioacetamide on chromosome-associated proteins in rat liver

This report deals with the isolation and analysis of liver cell nuclei from rats receiving thioacetamide daily. After 11 days of treatment, there is a decrease in the bound saline-soluble protein, no change in the phosphate-soluble protein, and a substantial increase in the histone fraction, these protein fractions being extracted in that order from the isolated nuclei. There is also an increase in the residue protein remaining after these extractions.

Studies on plasma membranes I. Chemical composition and enzyme content of plasma membranes isolated from rat liver

Plasma membranes were isolated from rat liver. Electron microscopy showed that the preparations were not contaminated by other identifiable cellular components. Antibodies prepared against the isolated membranes were preferentially fixed by the plasma membranes of liver tissue. Chemically the plasma membranes consisted of a phospholipoglycoprotein core, mainly composed of components of a mol. wt. of about 10 000, to which saline-soluble proteins were attached. The latter were positively charged at neutral pH and contained four antigenically-active proteins. The protein, choline, phospholipid-P, cholesterol, hexose, hexosamine, sialic acid and sulphydryl content of the isolated membranes was measured and expressed in relation to the membrane-bound P, which consisted virtually completely of phospholipid P. Next to arylesterase (EC 3.1.1.2), NADH 2-cytochrome c reductase (EC 1.6.2.1) and a trace of NAD nucleosidase (EC 3.2.2.5) activity, the enzymes found present in the isolated plasma membranes were of phosphate-ester-splitting types, viz., alkaline and acid phosphomonoesterases (EC 3.1.3.1 and EC 3.1.3.2), phosphodiesterase (EC 3.1.3.2), ribonuclease(s) (EC 2.7.7.16), glucose 6-phosphatase (EC 3.1.3.9), NAD pyrophosphatase (EC 3.6.1.9), Mg 2+-ATPase (EC 3.6.1.4), Na +-K +-Mg 2+- ATPase, 5′-mononucleotidase (EC 3.1.3.5) and a trace of ADPase (EC 3.6.1.6). The specific activities of these enzymes were either much lower or much higher than those of the corresponding enzymes found in microsomal preparations. The possibility that the plasma-membrane preparations were contaminated by microsomal elements is discussed, and, on account of the available evidence, the conclusion is reached that there is no reason to assume that this was the case.

Saline-soluble proteins of isolated thymus nuclei

The saline extract of isolated thymus nuclei was found to contain a number f proteins in addition to the ribonucleoprotein. Ultracentrifugal studies of the whole saline extract and these proteins showed that pH or salting-out with ammonium sulfate affected aggregation of some of the protein species. A tentative fractionation of these proteins was also attempted. Some of the characteristics of the nuclear saline extract fractions was discussed.

Incorporation and conversion of lysine-2-C14 in rat biopsy-connective tissue.

Summary1. C14-labeled lysine administered intraperitoneally into the rat is incorporated within hours into the saline-soluble and -insoluble non-collagenous protein and collagen of biopsy-connective tissue. Radioactivity is confined to lysine in all fractions of connective tissue except for a portion which is converted to hydroxylysine in the collagen. 2. Following appearance of radioactivity in all fractions of connective tissue, decay occurs rapidly in saline-insoluble non-collagenous protein and saline-soluble protein and slowly in the collagen fraction. Thirty days after injection of labeled lysine approximately 10% of maximum activity remained in the saline protein fractions while 30% remained in collagen. 3. Incorporation of labeled lysine into the non-collagenous protein of connective tissue is not influenced by tissue age while its incorporation into the collagen appears to decrease with tissue age. 4. Specific activity of labeled hydroxylysine from a 300-day old tissue of a female rat was approxi...