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Biomedical subjects

A Zaheer

Publications and source records attributed to A Zaheer.

48 records · Page 3Linked to original sources
PubMed1981

(Na+ + K+)-stimulated ATPase inhibition by cesalin and macromomycin.

(Na+ + K+)-stimulated ATPase was purified from dog kidney and its catalytic and glycoprotein subunits were separated. The enzymatic activity of the ATPase was totally inhibited by ouabain and partially inhibited by cesalin, maromomycin, concanavalin A, and wheat germ agglutinin. The inhibitions by cesalin or macromomycin can be reversed by the addition of phosphatidylethanolamine or phosphatidylserine, but not phosphatidylcholine. The specific binding of 125I-cesalin to the enzyme was inhibited by concanavalin A, wheat germ agglutinin, macromomycin, and the antibodies prepared in rabbits against the holoenzyme and the glycoprotein subunit, but not by ouabain, simple sugars, or the antibody against the catalytic subunit. It is proposed that the antitumor activities of cesalin and macromomycin are initiated in part by their binding to the glycoprotein subunit of (Na+ + K+)-ATPase in the plasma membrane.

Adenocarcinoma↗
PubMed1980

Comparative study of three basic polypeptides from snake venoms in relation to their effects on the cell membrane of normal and tumor cells.

Basic polypeptides producing a variety of effects on animals and cells have been isolated from snake venoms. Many possess common structural features and also produce similar pharmacological effects. This has led to doubt as to the specificity of each polypeptide. Study of toxin gamma (cardiotoxin from Naja nigricollis), cytotoxin P6 (from naja naja, preferentially cytotoxic to certain cells) and neurotoxin alpha (Naja nigricollis) under identical conditions shows that they are separate entities though having some common structural properties. The amino acid composition shows certain resemblance between the nontoxic polypeptides, P6 and toxin gamma, as compared to the neurotoxin alpha. Their molecular weights are of the same order. Sulphydryl groups are absent in all but they possess a high proportion of disulphide linkages. The behavior of toxin gamma, cytotoxin P6 and neurotoxin alpha on Yoshida sarcoma cells and human erythrocytes demonstrate that whereas cytotoxin P6 was more active in lysing Yoshida sarcoma cells the order of activity was reversed in the human erythrocytes. Apparently these two cell systems respond differently to the action of the two polypeptides suggesting that they bind to different membrane receptors. The selectively displayed in changing the membrane permeability of different cells is probably dependent not ony on their basic charge but on the specificity of their protein structure.

Amino Acids↗
PubMed1980

Gamma-irradiation studies with synthetic poly-L-serine in the megarad dose range.

Gamma irradiation of poly-L-serine was carried out in dilute aqueous solutions (50 micrograms/ml) in the dose range 0.44-2.64 megarad. Damage to the peptide bond studied through u.v. spectral absorption and gel filtration on a Sephadex G50 column and damage to the serine side groups through t.l.c. and amino acid analysis of the hydrolyzed samples indicate higher radiosensitivity of the side groups as compared to that of the peptide bond even in the megarad range. Early damage to the serine side groups seems to result in the formation of glycine.

Amino Acids↗
PubMed1979

Inactivation of membrane-bound (Na+ +K+)-ATPase of Yoshida sarcoma cells and cobra venom cytotoxin complex with the glycolipid components of the enzyme system.

The molecular mechanisms involved in the inactivation of (Na+ + K+)-stimulated ATPase of Yoshida sarcoma cells by a cytotoxic protein (P6) from cobra venom have been examined. The overall data obtained using purified (Na+ + K+)-stimulated ATPase of Yoshida sarcoma cells suggest that cytotoxin P6 combines with phosphatidyl serine and a glycolipid which are closely associated with (Na+ + K+)-stimulated ATPase which in turn may lead to the inactivation of the enzyme in this cell system.

Animals↗
PubMed1979

Influence of charge on the inactivation of membrane bound (Na+ + K+)-ATPase of Yoshida sarcoma cells by inhibitor proteins from cobra venom.

Inactivation of (Na+ + K+)-ATPase of Yoshida sarcoma cells and beef brain microsomes by phospholipase A2 and a cytotoxin P6 from snake venom has been examined in relation to their activity to degrade phospholipids. Cytotoxin P6 which was most basic and devoid of phospholipase activity was most effective in inhibiting the (Na+ + K+)-ATPase of Yoshida sarcoma cells. Phospholipase A2 from Naja naja which was most active in degrading phospholipids was least effective in inhibiting (Na+ + K+)-ATPase in Yoshida sarcoma cells or in beef brain microsomes. Addition of trace amounts of cytotoxin P6 to the phospholipase considerably enhanced the inactivation of (Na+ + K+)-ATPase. The evidence suggests that the charge of the inhibitor protein and its specific structure play an important role in the inactivation of (Na+ + K+)-ATPase.

Animals↗
PubMed1975

Inactivation of (Na-++K-+)-stimulated ATPase by a cytotoxic protein from cobra venom in relation to its lytic effects on cells.

The mechanism of action of the cytotoxic protein P6 isolated from cobra venom (Naja naja) which shows preferential cytotoxicity particularly to Yoshida sarcoma cells has been studied by its effects on the membrane-bound enzyme (Na-++K-+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) of a variety of cell systems. Evidence obtained with Yoshida sarcoma cells, dog and human erythrocytes and three tissue culture cell lines KB (human oral carcinoma), Hela (human cervix carcinoma) and L-132 (human lung embryonic) shows that inhibition of (Na-++K-+)-ATPase by the P6 protein can be correlated with its lytic activity. (Na-++k-+)-ATPase of Yoshida sarcoma membrane fragments inactivated by P6 protein could be reconstituted by the addition of phosphatidylserine and phosphatidic acid. It is conceivable that lysis of cells by the P6 protein may be due to an imbalance of K-+ and Na-+ in the cell which leads to swelling and disintegration of the membrane structure. Observations indicate that the P6 protein combines with membrane constituents of susceptible cells. The overall evidence suggests that both the specificity of its protein structure and the highly basic nature of the P6 protein are factors which enable it to compete with the lipid moiety maintaining the (Na-++k-+)-ATPase of the susceptible cells in proper conformation for activity.

Adenosine Triphosphatases↗