L-cell growth stimulation by a beta-casein peptide: the importance of its phosphorylation site for activity.

L-cell proliferation was markedly enhanced by addition to the medium of a synthetic peptide corresponding to residues 1-18 of human beta-casein. Experiments using several synthetic peptides of decreasing length demonstrated that L-S-S-S-E-E (residues 7-12), a major phosphorylation site in beta-casein, appeared to be important for the activity. The phosphorylated beta-casein peptide showed no activity. Recent findings have demonstrated that a similar sequence, S-E-E-E or S-D-D-E, is commonly present in many oncoproteins derived from nuclear oncogenes such as myc, myb and E1A, and plays an important role in transformation functions. The beta-casein peptide may affect mammalian cell proliferation through a modification of of the oncoprotein functions.     

Sequence of three members and expression of a new major subfamily of glutelin genes from rice

Three members have been isolated of an additional glutelin gene subfamily, named subfamily B, consisting of about five members per haploid rice genome. Restriction fragment length polymorphism analysis showed major differences between Japonica and Indica lines, indicating the divergence of the subfamily since the split between the two varieties. While corresponding exons of the subfamily B showed 80 to 88% nucleotide sequence homology, those exons were only 60–65% homologous to those of the glutelin A subfamily [15, 19, 24], distinguishing them from the subfamily A. Intron position and derived polypeptide structure, in addition to the nucleotide sequence, confirm the subfamily B members as glutelins. Analysis of RNA from seeds of different stages of development showed that the subfamily B members were expressed at the same time as those of subfamily A, demonstrating coordinated regulation of the two subfamilies.     

S100a0 (alpha alpha) protein in cardiac muscle. Isolation from human cardiac muscle and ultrastructural localization

S100 protein, an acidic and calcium-binding protein, was believed to be localized in the nervous tissue, but recently it has been reported to be mainly present in the cardiac and the skeletal muscles of various mammals in the alpha alpha form (S100a0) at much higher levels than the nervous tissues. We isolated here S100 protein from human cardiac muscles. The isolated cardiac muscle S100 protein showed a single band on electrophoresis at the same position as that of human skeletal muscle S100a0. The amino acid composition of the purified S100 protein was quite similar to that of human skeletal muscle S100a0 or bovine brain S100a0. The immunohistochemical study by use of antibodies monospecific to the alpha subunit of S100 protein (S100-alpha) revealed that S100-alpha was strongly labeled in human myocardial cells, whereas the beta subunit of S100 protein (S100-beta) was not detected in the cells. These results suggest that a predominant form of S100 protein in human myocardial cells is not S100a (alpha beta) or S100b (beta beta), but S100a0 (alpha alpha). In order to determine the ultrastructural localization of S100a0 in mouse cardiac muscle, the direct peroxidase-labeled antibody method was employed. S100a0 was mainly localized in the polysomes in the interfibrillar spaces, the fine filamentous structure of the Z line and fascia adherens of the intercalated disc and in the lumen of junctional sarcoplasmic reticulum.     

Plasmodium falciparum: gene structure and hydropathy profile of the major merozoite surface antigen (gp195) of the Uganda-Palo Alto isolate

The gene encoding the 195,000-Da major merozoite surface antigen (gp195) of the FUP (Uganda-Palo Alto) isolate of Plasmodium falciparum, a strain widely used for monkey vaccination experiments, has been cloned and sequenced. The translated amino acid sequence of the FUP gp195 protein is closely related to the sequences of corresponding proteins of the CAMP (Malaysia) and MAD-20 (Papua New Guinea) isolates and more distantly related to those of the Wellcome (West Africa) and K1 (Thailand) isolates, supporting the proposed allelic dimorphism of gp195 within the parasite population. The prevalence of dimorphic sequences within the gp195 protein suggests that many gp195 epitopes would be group-specific. Despite the extensive differences in amino acid sequence between gp195 proteins of these two groups, the hydropathy profiles of proteins representative of both groups are very similar. The conservation of overall secondary structure shown by the hydropathy profile comparison indicates that gp195 proteins of the various P. falciparum isolates are functionally equivalent. This information on the primary structure of the FUP gp195 protein will enable us to evaluate the possible roles of conserved, group-specific and variable epitopes in immunity to the blood stage of the malaria parasite.     

Induction of S100 protein in 3T3-L1 cells during differentiation to adipocytes and its liberating by lipolytic hormones

When confluent cultures of cloned mouse 3T3-L1 cells were differentiated to adipocytes by three days of treatment with a combination of 0.5 microM dexamethasone and 0.5 mM 1-methyl-3-isobutylxanthine, the S100 protein content in the cells increased markedly, as determined by a sensitive immunoassay system. The S100 protein induced in the cell was the alpha alpha form (S100ao), which is the predominant form of S100 protein in mouse adipose tissue. The S100ao concentration in preadipocytes was about 1-3 ng/mg protein, while the concentration in differentiated adipocytes was 60-200 ng/mg protein. The immunoblotting test of the crude extract of adipocytes confirmed that the immunoreactive substance in the cells was the alpha subunit of S100 protein. The treatment with 1-methyl-3-isobutylxanthine or dexamethasone alone neither elicited the S100 protein induction nor triacylglycerols accumulation in the cells. The accumulation of triacyglycerols in the cells was always preceded by the induction of S100ao protein under conditions where the differentiation to adipocytes was elicited. The induction of S100ao protein and accumulation of triacylglycerols in the cells treated with dexamethasone and 1-methyl-3-isobutylxanthine were inhibited by the addition of antimicrotubular drugs, colchicine and vinblastine, but not by cytochalasin B, an antimicrofilament drug. S100ao protein in 3T3-L1 adipocytes was released by incubation with a lipolytic hormone, adrenocorticotropic hormone or catecholamines, in a cyclic-AMP-dependent manner as observed with rat epididymal fat pads [Biochim. Biophys. Acta (1986) 889, 84-90]. These results also suggest that S100 protein may participate in the function of adipocytes.     

Phorbol esters enhance attachment of NIH/3T3 cells to laminin and type IV collagen substrates

The effect of phorbol esters on the adhesive properties of NIH/3T3 mouse fibroblasts was investigated using plastic substrates precoated with the extracellular matrix proteins fibronectin, collagen, and laminin. Treatment with phorbol 12-myristate 13-acetate (PMA) enhanced NIH/3T3 cell attachment to laminin and type IV collagen substrates but had little or no effect on attachment to fibronectin and type I collagen substrates. The effect of PMA in enhancing cell attachment to laminin and type IV collagen substrates was dose dependent between 10(-9) and 10(-7) M. PMA was effective as early as 30 min; the effect reached a maximum at 2 h and decreased gradually. Phorbol 12, 13-dibenzoate and phorbol 12, 13-diacetate were effective but to a lesser extent and phorbol 12-myristate and phorbol 13-acetate showed little or no effect. These results suggest that PMA may enhance NIH/3T3 cell adhesion through effects on laminin and type IV collagen receptors. Retinoic acid, which itself requires at least 6 h to show an effect on attachment, did not have any effect on cell attachment in 2 h and, if anything, slightly inhibited PMA-enhanced cell attachment to laminin and type IV collagen substrates.     

Human atrial natriuretic polypeptide in plasma of patients with anorexia nervosa

To examine the effects of chronic dehydration and starvation on plasma levels of human atrial natriuretic polypeptide (hANP) in human subjects, the basal level and saline-induced rise of plasma hANP in 7 patients with anorexia nervosa were compared with those in age-matched healthy subjects. The unstimulated level of plasma hANP was markedly high in the patients with anorexia nervosa (patients vs. control; 55.4 +/- 9.0 pg/ml vs. 11.4 +/- 6.1 pg/ml, P less than 0.01). However, no significant increase of plasma hANP in the anorectic patients was observed in response to saline-infusion, while a 3-fold increase over the basal level of plasma hANP was noted in the saline-infused normal young subjects. These results show that hANP may be secreted to an inadequate extent, hence the release would be resistant to volume-loading. The pathophysiological meaning of such a high plasma concentrations of hANP in anorexia nervosa is the subject of ongoing studies.     

Gene organization in the region containing a new gene involved in chromosome partition in Escherichia coli.

A new mutation, parC, causing abnormal chromosome segregation was identified in two thermosensitive mutants of Escherichia coli. The thermosensitive growth of the mutants was corrected by pLC4-14 in the Clarke-Carbon collection. This plasmid carries a putative gene which can suppress the cell division defect due to ftsI (pbpB) and has hence been termed sufI (sui). The nearness of parC to metC was confirmed, and cotransduction frequency of parC was 59% with metC and 20% with glc. The parC-sufI region was analyzed by subcloning the chromosome region of pLC4-14. The parC and the sufI gene products were electrophoretically identified as proteins of 75 and 55 kilodaltons (kDa), respectively. The allelism of parC+ on pLC4-14 to parC1215 was confirmed by cloning parC1215. The sufI gene appeared to be dispensable for cell viability, and overproduction of its product caused suppression of ftsI. An essential gene coding for a 25-kDa protein was found between the parC and the sufI gene. These three genes were transcribed in the same direction and may be organized into an operon, with parC to the proximal side and with internal promoters at least for the distal genes. The localization of the gene products was examined in maxicells. The sufI protein was synthesized as a precursor which could be chased into a mature form. The major part of the mature form was found in the soluble fraction. The 25-kDa protein was found almost exclusively in the membrane fraction. The parC protein was associated with the membrane fraction in the presence of Mg2+ but found in the soluble fraction when Mg2+ was sequestered with EDTA.