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M Basu

Publications and source records attributed to M Basu.

105 records · Page 6Linked to original sources
PubMedDate not supplied

42,000-molecular weight EGF receptor has protein kinase activity.

The epidermal growth factor (EGF) receptor and other growth factor receptors have been shown to possess tyrosine-specific protein kinase activity. Before the demonstration of kinase activity in growth factor receptors, tyrosine kinases of molecular weight (MW) 60,000 (60K) were found to be encoded by the src oncogene and other oncogenes related to src. Our earlier work on intracellular processing of the EGF receptor, a 170,000-MW polypeptide, provided evidence for proteolytic separation of well defined structural domains, and suggested to us the possibility of separating functional domains by limited proteolysis. The isolation of such kinase domains should facilitate comparison of the receptor/kinase with other well characterized kinases including those of oncogene origin. We report here the identification of a catalytically functional 42K kinase derived proteolytically from the isolated human EGF receptor. This fragment, comparable in size to pp60src, carries the kinase ATP-binding site, and functions catalytically even after detachment from the EGF-binding site and the major autophosphorylation region.

Adenosine Triphosphate↗
PubMedDate not supplied

EGF receptor-associated DNA-nicking activity is due to a Mr-100,000 dissociable protein.

The receptor for epidermal growth factor (EGF) is a single-chain transmembrane polypeptide of relative molecular mass (Mr) 170,000 (170K) which has been implicated in the regulation of both normal and abnormal cell proliferation. It has an externally facing EGF-binding domain and a cytoplasmically facing tyrosine-specific protein kinase site. Although the receptor has been well characterized, the mechanism by which it transmits the growth stimulatory signal from the plasma membrane to the nucleus is unclear. EGF binding to cells has been shown to enhance topoisomerase activity within the cells. Topoisomerases catalyse the interconversion of topological isomers of DNA and thus may influence replication and transcription. Mroczkowski et al. reported that purified EGF receptors of both human and murine origin can nick supercoiled double-stranded (ds) DNA in an ATP-dependent fashion, an activity related to those of topoisomerases. Another related tyrosine kinase, pp60src, has also been reported to have a similar DNA-nicking activity. We have now characterized the EGF receptor-associated DNA-nicking activity by sucrose gradient centrifugation. Our results, presented here, indicate that the DNA-nicking activity is not intrinsic to the EGF receptor, but is found in a distinct molecular species.

DNA Topoisomerases, Type I↗
PubMedDate not supplied

(Dr. P. C. Sen Award on rural health practice). Infant and early childhood mortality in some rural ICDS blocks of west Bengal.

This one year prospective study was carried out to determine the CBR, CDR and different underfive mortality rates in some selected rural ICDS blocks of West Bengal and also to find out the common causes of infant and childhood mortality in these areas. It was revealed that most of the above mentioned indicators in ICDS blocks were considerably lower than that of National figures, but more or less similar to those of rural Bengal as recorded in routine Govt. reports. Compared to the picture of rural West Bengal, both still birth & perinatal mortality rates were found higher in all ICDS blocks. The causes of mortality trends among under fives' were found similar to that of rural India pattern i.e. prematurity, acute respiratory infections and diarrhoea being the leaders. Neonates, who contributed the largest share of infant mortality died mainly due to prematurity. So, observations like high perinatal mortality & still birth rates, huge proportion of neonatal death during infancy, same IMR but low 5MR, and death of neonates due to prematurity etc. claim the necessity of improving maternal component of ICDS services, their nutritional care in particular.

Birth Rate↗
PubMedDate not supplied

Cloning and expression of SAT-3 involved in SA-Le(x) biosynthesis: inhibition studies with polyclonal antibody against GST-SAT-3 fusion protein.

The SAT-3 activity (CMP-NeuAc:Gal beta 1-4GlcNAc beta 1-3 Gal beta 1-4Glc-ceramide alpha 2-3 sialytransferase) involved in the biosynthesis of sialy Le(x) has been characterized in human colon carcinoma cells and embryonic chicken brains. Using RT-PCR-based strategy, we have isolated partial cDNA clones of SAT-3 from ECB and Colo-205 mRNAs. Suitable primers from sialylmotif and N-terminal sequence of human placenta SAT-3 (HP-SAT-3) were used. The 800 bp cDNA fragment encoding a region (90%) of alpha 2-3 sialyltransferase (SAT-3) catalytic domain from ECB has been expressed as a glutathione S-transferase (GST) soluble fusion protein (62 kDa) in E. coli and purified over glutathione-agarose affinity matrix. Polyclonal antibody has been produced against affinity-purified catalytic domain of SAT-3 (GST-SAT-3 fusion protein). A concentration-dependent polydonal antibody binding to native SAT-3 has also been demonstrated by measuring the residual SAT-3 activity in the enzyme fractions from Colo-205. The marked inhibition (> 80%) of SAT-3 activity and relatively less inhibition (< 20%) of SAT-4 activity (CMP-NeuAc:GgOse4Cer alpha 2-3sialyl transferase) suggests strongly the existence of two different gene products (SAT-3 and SAT-4) in human colon carcinoma Colo-205 cells and in embryonic chicken brains (ECB).

Animals↗
PubMedDate not supplied

Ceramide glycanase from rat mammary tissues: inhibition by PPMP(D-/L-) and its probable role in signal transduction.

A ceramide glycanase (CGase activity has been characterized from lactating rat mammary tissue which cleaves the glycosidic bond between sphingosine and the glucose chain of a glycosphingolipid (GSL) thus liberating the intact oligosaccharide chain from a GSL. The majority (65%) of the hydrolase activity was detected in the supernatant fraction when the rat mammary tissue homogenate was centrifuged at 100,000 x g. Attempts to purify the enzyme indicated that the CGase protein is of hydrophobic nature as it binds to hydrophobic columns. The enzyme has been partially purified using hydrophobic columns in tandem. The partially purified protein was found to be immunoreactive to the antibody raised against the purified clam CGase. The immunostained band corresponded to a 64 kDa protein as also found with the clam enzyme. This immuno cross-reactivity indicated probable structural similarities between CGase proteins isolated from widely separated species in the evolutionary tree. The rat CGase was found to have a specific detergent requirement for optimal activity, and the pH optimum was found to be between 5 and 6. The enzyme activity is partially heat stable. It is not a divalent cation requiring enzyme; however, the activity is totally inhibited in the presence of mercury, indicative of a sulfhydryl group in the active site of the enzyme. The rat mammary CGase activity is inhibited in the presence of both D- and L-PPMP (1-phenyl-2-hexadecanoylamino-3-morpholino-1-propanol. HCl), homologs of PDMP (1-phenyl-2-decanoylamino-3-morpholino-1-propanol. HCl), a well-known inhibitor of GlcT-1 (Ceramide: UDP-Glc Glucosyltransferase), an enzyme in the glycolipid synthetic pathway. The inhibition seems to be of a competitive nature and the same type of inhibition is also observed with clam CGase. The CGase activity was found to be highest in lactating tissue compared to the activity found in either pregnant or post-lactating rat mammary tissues. Tissue survey indicated the presence of high levels of CGase in lactating rat liver, uterus, and ovary; moderate activity was detected in kidney and spleen. Both virgin and male rat mammary tissue also indicated a basic level of CGase activity. However, newborn spleen and mammary tissue showed a comparable level of activity to that found in lactating rat tissues. This report is mainly concerned with the characterization of CGase activity from a mammalian source and its importance in cellular processes.

Animals↗