Characterization of a high molecular weight protective antigen ofPlasmodium yoelli

SUMMARYA 230000 molecular weightPlasmodium yoeliiprotective antigen was characterized. Two monoclonal antibodies againstP. yoeliiimmunoprecipitated the 230000 mol. wt protein and a number of lower molecular weight polypeptides. These polypeptides were shown by peptide mapping and specific antibody binding to be fragments of the large protein. Iodination experiments suggested that the lower molecular weight species may be present on the surface of the merozoite. The protein was found not to be glycosylated. By serology, related antigens were shown to be associated with blood-stage schizonts ofP. vinckeisubspp.,P. chabaudisubspp. andP. falciparum.

Substrate stabilization of the palmitoyl-coenzyme A hydrolase activity of rat submaxillary gland

The long-chain acyl-CoA hydrolase (EC 3.1.2.2) activity of rat submaxillary salivary gland, found in the postmicrosomal supernatant fraction, has a pH optimum of 7.4. This hydrolase activity was found to be extremely labile, but inclusion of glycerol or the substrate palmitoyl-CoA in the preparations markedly stabilized the activity. Gel-filtration studies revealed multiple forms of the hydrolase, a lower-molecular-weight species of approx. 45 000 and a higher-molecular-weight species of approx. 130 000 observed when glycerol (20%, v/v) or palmitoyl-CoA (10 micro M) were included in the eluting buffer. This phenomenon is similar to that observed with the palmitoyl-CoA hydrolase of rat brain, except that there is no evidence that the higher-molecular-weight species of the hydrolase of submaxillary gland is generated by substrate-induced dimerization of the lower-molecular-weight species.

Studies on the assembly of the rat lens capsule. Biosynthesis and partial characterization of the collagenous components

1. Isolated rat lens capsules synthesized hydroxy[3H]proline-containing polypeptides when incubated with [3H]proline. 2. The collagenous polypeptides synthesized during a 2 h incubation were analyzed by both gel-filtration chromatography and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and shown to have an apparent mol.wt. of approx. 180,000. 3. No evidence was obtained for conversion of these polypeptides into a lower-molecular-weight species in experiments where capsules were labelled for 2 h and chased with non-radioactive proline for up to 22 h. However, a time-dependent incorporation of the 180,000-mol.wt. species into a larger collagenous component was observed and this could be prevented by the inclusion of beta-aminopropionitrile in the incubation medium. 4. The radioactive components synthesized by the capsules correspond to subunits of the intact lens capsule and the direct incorporation of the polypeptide of mol.wt. 180,000 into deoxycholate-insoluble basement membrane was demonstrated.

Histone phosphatase and cyclic nucleotide-stimulated protein kinase from human lymphocytes

1. Extracts of human peripheral blood lymphocytes contained a histone phosphatase that catalysed the release of Pi from phosphorylated whole thymus histone. 2. Stimulation of the phosphatase was obtained by concentrations of KCl and NaCl of up to 75mm, and by MgCl2; CaCl2 inhibited the enzymic activity. 3. In the absence of MgCl2, phosphoenol-pyruvate inhibited histone phosphatase activity; this inhibition could be partially reversed by adding MgCl2 to assays. 4. Lymphocyte extracts contained a protein kinase activity which was maximally stimulated by 1μm-cyclic AMP (adenosine 3′:5′-cyclic monophosphate) or by 0.1mm-cyclic GMP (guanosine 3′:5′-cyclic monophosphate). 5. Incubation of the enzyme with histone in the absence of ATP or MgCl2 resulted in the dissociation of the enzyme into a lower-molecular-weight species that was not stimulated by cyclic AMP. This effect could be prevented if ATP and MgCl2 were present in reaction mixtures before histone and enzyme were allowed to interact. 6. Cyclic AMP also dissociated the kinase into a lower-molecular-weight species. 7. In the presence of 1μm-AMP, half-maximal activities were obtained with 0.92mm-MgCl2, 6.0μm-ATP and 0.23mg of whole thymus histone/ml.