Search PubMed⌕ Search

Biomedical subjects

A Peterkofsky

Publications and source records attributed to A Peterkofsky.

108 records · Page 6Linked to original sources
PubMed1972

Glutamic acid as a precursor to N-terminal pyroglutamic acid in mouse plasmacytoma protein (protein synthesis-initiation-immunoglobulins-pyrrolidone carboxylic acid).

Cell suspensions derived from a mouse plasmacytoma (RPC-20) that secretes an immunoglobulin light chain containing N-terminal pyroglutamic acid can synthesize protein in vitro. Chromatographic examination of an enzymatic digest of protein labeled with glutamic acid shows only labeled glutamic acid and pyroglutamic acid; hydrolysis of protein from cells labeled with glutamine, however, yields substantial amounts of glutamic acid in addition to glutamine and pyroglutamic acid. The absence of glutamine synthetase and presence of glutaminase in plasmacytoma homogenates is consistent with these findings. These data indicate that N-terminal pyroglutamic acid can be derived from glutamic acid without prior conversion of glutamic acid to glutamine. Since free or bound forms of glutamine cyclize nonezymatically to pyroglutamate with ease, while glutamic acid does not, the data suggest that N-terminal pyroglutamic acid formation from glutamic acid is enzymatic rather than spontaneous.

Amino Acyl-tRNA Synthetases↗
PubMed1971

Glucose and the metabolism of adenosine 3':5'-cyclic monophosphate in Escherichia coli.

Measurements of adenosine 3':5'-cyclic monophosphate (cAMP) concentrations have been made in Escherichia coli under various conditions. Different strains of E. coli accumulate different extracellular concentrations of cAMP (0.2-4 mum) at stationary phase. Mutation at the RNA control locus does not affect the accumulation pattern. Growth of the bacteria in minimalsalts medium leads to a greater accumulation of cAMP than growth in nutrient broth. Partition studies show that essentially all of the cAMP that is accumulated is found in the medium rather than in the cells. Kinetic studies show that most of the cAMP is formed coincidentally with exhaustion of glucose from the medium. Growth on high concentrations of glucose leads to inhibition of cAMP formation. Other carbon sources cannot substitute for glucose in this inhibitory effect. Measurements of enzyme activities indicate that glucose suppression of cAMP formation cannot be accounted for by a decreased activity of adenylate cyclase or an increased activity of cAMP phosphodiesterase (EC 3.1.3.7).

Adenylyl Cyclases↗
PubMedDate not supplied

Specific binding to adrenal particulate fraction of cyclo(histidyl-proline), a TRH metabolite.

Histidyl-proline diketopiperazine (cyclo(His-Pro), a metabolite of the neuropeptide thyrotropin releasing hormone, has been shown to possess intrinsic biological activities. The binding of this peptide to various tissue particulate preparations was investigated. While the peptide showed no apparent binding to particulate fractions derived from brain, pituitary, and some other tissues, binding to adrenal and liver was demonstrated. The binding of cyclo(His-Pro) to bovine adrenal cortical particles was further characterized. Binding at equilibrium was greater at 4 degrees C than at 37 degrees C. The binding was dependent on tissue concentration, showed a pH optimum between 7 and 8, and was inactivated by treatment of the particulate fraction with trypsin or by boiling. The interaction of cyclo(His-Pro) with the tissue was not associated with any metabolism of the peptide. Kinetic studies of association of cyclo(His-Pro) with adrenal cortical particles indicated a single class of binding sites with a KD of approximately 900 nM and a maximum number of sites of 92 pmoles/mg protein. The binding was stereospecific and the histidine moiety of the peptide was the major determinant of the binding. A variety of catechols, serotonin and histamine competed with cyclo(His-Pro) for binding with IC50's ranging from 17-450 muM. Cyclo(His-Pro) did not affect monoamine oxidase or adenylate cyclase activity in adrenal cortical particulate preparations.

Adrenal Cortex↗
PubMedDate not supplied

Overproduction and rapid purification of the phosphoenolpyruvate:sugar phosphotransferase system proteins enzyme I, HPr, and Protein IIIGlc of Escherichia coli.

We present methods for the rapid, simple purification of Enzyme I, HPr, and Protein IIIGlc of the Escherichia coli phosphoenolpyruvate:sugar phosphotransferase system (PTS) using plasmids overproducing gene products. The gene for HPr (ptsH) was cloned into the expression vector pKC30. A simple procedure was devised for the purification to homogeneity of this protein from extracts of heat-induced cells containing pKC30/ptsH recombinant clone. The genes for Enzyme I (ptsI) and Protein IIIGlc (crr) were cloned separately into the expression vector pRE1. Rapid purification procedures were developed for the isolation of homogeneous preparations of these two proteins from extracts of heat-induced cells containing pRE1/ptsI and pRE1/crr recombinants. From about 6 g of cells, these procedures yielded 100, 86, and 50 mg of Enzyme I, HPr, and Protein IIIGlc, respectively. The activity of the proteins purified by these methods was comparable to that of the proteins isolated by previously published less efficient procedures.

Base Sequence↗