Evidence for the subcellular localization and specificity of chlordane inhibition in the marine bacterium Aeromonas proteolytica.

Sublethal levels (10 to 100 micrograms/ml) of the chlorinated insecticide chlordane (1,2,4,5,6,7,8,8-octachloro-3a,4,7,7a-tetrahydro-4,7-methanoindan) were introduced into the growth medium of the marine bacterium, Aeromonas proteolytica. Chlordane inhibited the synthesis of an extracellular endopeptidase by almost 40% but exhibited no such inhibition of the extracellular aminopeptidase also produced during the growth cycle. Studied with 14C-labeled chlordane demonstrated that the insecticide was not biologically degraded under the test conditions used and that up to 75% of the recoverable chlordane was cell associated within 48 h. Studied with uniformly labeled L[14C]valine and [2-14C]uracil established that neither the transport nor the incorporation of these protein and ribonucleic acid precursors was inhibited by chlordane. Separation of the membrane fractions using isopycnic centrifugation localized 14C-labeled chlordane in the cytoplasmic membrane. Also, chlordane inhibited the membrane-bound adenosine 5'-triphosphatase while the soluble (released) form of this enzyme remained unaffected. These data indicate that chlordane resides in the cytoplasmic membrane and may cause specific alterations in membrane-associated activities.     

The first seven amino acids encoded by the v-src oncogene act as a myristylation signal: lysine 7 is a critical determinant.

The transforming protein of Rous sarcoma virus, pp60v-src, is covalently coupled to myristic acid by an amide linkage to glycine 2. Myristylation promotes the association of pp60v-src with cellular membranes, and this subcellular location is essential for transforming activity. The findings presented here, in conjunction with the previous reports of others, imply that the seventh amino acid encoded by v-src might be important in the myristylation reaction. Replacement of lysine 7 by asparagine greatly reduced the myristylation, membrane association, and transforming activity of pp60v-src. In contrast, substitution of arginine at residue 7 had no effect on any of these properties of pp60v-src. Addition of amino acids 1 to 7 encoded by v-src was sufficient to cause myristylation of a src-pyruvate kinase fusion protein. We conclude that the recognition sequence for myristylation of pp60v-src comprises amino acids 1 to 7 and that lysine 7 is a critical component of this sequence.     

Analysis of the form of cortical neuron reaction to acetylcholine

Reaction patterns of 90 cortical neurons to acetylcholine approximated by two parabolas have been divided on simple and complex. The participation of different types of cholinoreceptors in complex reactions to transmitter is proposed.     

Guanosine 5'-triphosphate binding protein (Gi) and two additional pertussis toxin substrates associated with muscarinic receptors in rat heart myocytes: characterization and age dependency

The coupling of muscarinic receptors with G-proteins was investigated in cultured myocytes prepared from the hearts of newborn rats. The coupling was investigated in both young (5 days after plating) and aged (14 days after plating) cultures, in view of the completely different effects of 5'-guanylyl imidodiphosphate [Gpp(NH)p] on muscarinic agonist binding to homogenates from young vs aged cultures [Moscona-Amir, E., Henis, Y. I., Yechiel, E., Barenholz, Y., & Sokolovsky, M. (1986) Biochemistry 25, 8118-8124]. Pretreatment of cultures from both ages by Bordetella pertussis toxin (IAP) was found to eliminate any Gpp(NH)p effect on carbamylcholine binding. IAP by itself induced a rightward shift in the carbamylcholine competition curve in homogenates from aged cultures, but no such effect was observed in homogenates from young cultures. IAP-catalyzed [32P]ADP-ribosylation of membrane preparations from young and aged cultures revealed major differences between them. Young cultures exhibited a major IAP substrate at 40 kDa, which was also recognized by anti-alpha i antibodies, and two novel IAP substrates at 28 and 42 kDa, which were weakly ADP-ribosylated by the toxin and were not recognized with either anti-alpha i or anti-alpha o antibodies. In aged cultures, only the 40-kDa band (ribosylated to a lower degree) was detected. The parallel age-dependent changes in the three IAP substrates (28, 40, and 42 kDa) and in the interactions of the G-protein(s) with the muscarinic receptors strongly suggest close association between the two phenomena. All of these age-dependent changes in the G-protein related parameters were prevented by phosphatidylcholine-liposome treatment of the aged cultures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative analysis of the HBsAg level in human blood preparations

A total of 218 batches of blood preparations produced from different raw materials have been studied by means of enzyme immunoassay kits (Abbott Laboratories, USA). The assays have revealed that the preparations under study are nonstandard with respect to the content and isolation rate of HBsAg, the marker of hepatitis B virus. These data necessitate search for the ways of improving the quality of blood preparations.