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Biomedical subjects

D D Chaplin

Publications and source records attributed to D D Chaplin.

98 records · Page 6Linked to original sources
PubMed1979

Protein phosphorylation in human peripheral blood lymphocytes. Subcellular distribution and partial characterization of adenosine 3':5'-cyclic monophosphate-dependent protein kinase.

Cytoplasmic and membrane fractions prepared from human peripheral-blood lymphocytes both contained cyclic AMP-dependent protein kinase activity and endogenous protein kinase substrates. Protein kinase activity in the particulate fractions was not eluted with 0.25 M-NaCl, suggesting that it was not derived from non-specifically absorbed soluble cytoplasmic protein kinase. Nor was the particulate protein kinase activity eluted by treatment with cyclic AMP, suggesting that the catalytic subunit is membrane-bound and arguing against cyclic AMP-induced translocation of particulate activity. Cyclic AMP-dependent protein-phosphorylating activity in the cytoplasmic fraction was highly sensitive to inhibition by Mn2+, and was co-eluted from DEAE-cellulose primarily with type-I rabbit skeletal-muscle kinase. Cyclic AMP-dependent phosphorylating activity in the plasma-membrane fractions was stimulated at low [Mn2+] and inhibited only at high [Mn2+]. When solubilized with Nonidet P-40, plasma-membrane protein kinase was co-eluted from DEAE-cellulose with type-II rabbit muscle kinase. These differences, together with the strong association of the particulate kinases with the particulate fraction, suggest the possibility of compartmentalized protein phosphorylation in intact lymphocytes.

Caseins↗
PubMed1979

Protein phosphorlyation in human peripheral blood lymphocytes. Phosphorylation of endogenous plasma membrane and cytoplasmic proteins.

Phosphorylation of endogenous proteins in subcellular fractions of human peripheral-blood lymphocytes was studied by one- and two-dimensional polyacrylamide-gel electrophoresis. Studies using extensively purified subcellular fractions indicated that the endogenous phosphorylating activity in the particulate fractions was derived primarily from the plasma membrane. Electrophoresis of (32)P-labelled subcellular fractions in two dimensions [O'Farrell (1975) J. Biol. Chem.250, 4007-4021] provided much greater resolution of the endogenous phosphoproteins than electrophoresis in one dimension, facilitating their excision from gels for quantification of (32)P content. More than 100 cytoplasmic and 20 plasma-membrane phosphorylated species were observed. Phosphorylation of more than 10 cytoplasmic proteins was absolutely dependent on cyclic AMP. In the plasma membrane, cyclic AMP-dependent phosphoproteins were observed with mol.wts. of 42000, 42000, 80000 and 90000 and pI values of 6.1, 6.3, 6.25 and 6.5 respectively. Phosphorylation of endogenous cytoplasmic and plasma-membrane proteins was rapid with t((1/2))=5-12s at 25 degrees C. Between 40 and 70% of the (32)P was recovered as phosphoserine and phosphothreonine when acid hydrolysates of isolated plasma-membrane phosphoproteins were analysed by high-voltage paper electrophoresis. The presence of cyclic AMP-dependent protein kinase and endogenous phosphate-acceptor proteins in the plasma membranes of lymphocytes provides a mechanism by which these cells might respond to plasma-membrane pools of cyclic AMP generated in response to stimulation by mitogens or physiological modulators of lymphocyte function.

Blood Protein Electrophoresis↗
PubMed1974

The effects of thrombin on phytohemagglutinin receptor sites in human platelets.

We have previously demonstrated that lentil phytohemagglutinin (lentil-PHA) binds to human platelet membranes without causing either aggregation or the release reaction. When platelets are treated with thrombin, there is an increase in lentil-PHA binding suggesting the appearance of new receptor sites on the cell surface. We prepared a lentil-PHA-ferritin conjugate using affinity chromatography which was used to saturate cell surface receptor sites. Studies using this conjugate suggest that thrombin causes a complex change in the platelet surface involving a decrease in the number of lentil-PHA receptor sites on the external platelet surface with a marked increase in sites within the center of the canalicular system. These increased sites may result from fusion of granule membranes with the canalicular membranes during the secretion process. There is no obvious relationship between lentil-PHA receptor sites and intramembranous particles.

Binding Sites↗
PubMedDate not supplied

Two steroid 21-hydroxylase genes are located in the murine S region.

A common inherited disorder of steroidogenesis in man, 21-hydroxylase (21-OH) deficiency, is linked to the HLA major histocompatibility complex (MHC), and is associated in particular with certain allotypes of the HLA-linked complement proteins. Recently, this disorder was demonstrated to result from a defective structural gene for the 21-OH enzyme, also termed cytochrome P-450C21. The human (HLA) and murine (H-2) MHCs are homologous in overall organization and in the structures of their component genes. To determine whether 21-OH genes are located in the H-2 complex, we have now used a bovine adrenal complementary DNA clone encoding part of 21-OH to examine a cluster of overlapping cosmid clones derived from the S region of the BALB/c mouse. We found that there are two 21-OH genes in this region, located immediately 3' to the C4 and Slp genes.

Adrenal Cortex↗