Synthesis of surfactant-associated glycoprotein A by rat type II epithelial cells. Primary translation products and post-translational modification

Surfactant-associated glycoproteins A, 38 (A3), 32 (A2) and 26 (A1) kDa, pI (4.2-4.8), were identified as related proteins present in surfactant isolated from rat lung lavage fluid. Differences in size and charge among surfactant-associated glycoproteins A were related to differences in glycosylation as determined by reduction of the larger forms (38 and 32 kDa) to 26 kDa by endoglycosidase F and by increased isoelectric points of the glycosylated forms after treatment with neuraminidase. Synthesis and secretion of surfactant-associated glycoproteins A and precursors were demonstrated in purified rat Type II epithelial cells by immunoprecipitation of [35S]methionine-labelled proteins with anti-surfactant-associated glycoprotein A antisera. In pulse-chase experiments, labelled proteins 26-34 kDa, appeared within 10 min and smaller forms co-migrated with surfactant-associated glycoprotein A from alveolar lavage. The relative abundance of the larger molecular mass forms (30-34 kDa, pI 4.8) increased at later times up to 3 h. More acidic mature forms, which co-migrated with surfactant-associated glycoproteins A2 and A3 in surfactant (38 and 32 kDa), were readily detectable in the media, but were not abundant forms in lysates of labelled Type II cells after 1-3 h of incubation. Primary translation products of surfactant-associated glycoprotein A were immunoprecipitated with monospecific anti-surfactant-associated glycoprotein A antiserum after in vitro translation of poly(A)+ mRNA isolated from adult rat lung. The immunoprecipitated translation product migrated at 26 kDa, pI 4.8, and migrated slightly faster than surfactant-associated glycoprotein A1 from surfactant. Treatment of surfactant-associated glycoprotein A with bacterial collagenase resulted in proteolytic fragments 23-20 kDa, pI 4.2-4.8, which no longer underwent sulfhydryl-dependent cross-linking, suggesting that the collagen-like domain was required for the sulfhydryl-dependent oligomerization. Surfactant-associated glycoproteins A are synthesized by rat Type II epithelial cells as pre-proteins, 26-34 kDa. Larger forms result primarily from N-linked glycosylation of the 26 kDa primary translation product. Mature, more acidic forms result from further addition of sialic acid.     

Frequency among Enterobacteriaceae of the DNA sequences encoding type 1 pili.

Type 1 pili, characterized by mannose-inhibitable agglutination of fowl or guinea pig erythrocytes, have been found throughout the family Enterobacteriaceae. A radiolabeled probe was prepared from a restriction endonuclease-digested fragment of the Escherichia coli pil operon and used to detect homologous DNA sequences in 236 bacteria representing 11 genera of Enterobacteriaceae. Only isolates identified as E. coli or Shigella spp. exhibited homology. In contrast, mannose-sensitive hemagglutination was observed in nine genera. Probe DNA did not hybridize to plasmid DNA, indicating a chromosomal location for the pil operon. Analysis of restriction nuclease-digested whole-cell DNA from 60 E. coli and two Shigella sp. isolates indicated that internal sequences were conserved in most strains, but that changes in flanking sequences in the chromosome were common.     

Identification of canine pulmonary surfactant-associated glycoprotein A precursors

Surfactant-associated glycoproteins A were identified by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of crude surfactant from canine alveolar lavage: an unglycosylated form (protein A1), 27,000-28,000 daltons; glycoprotein A2, 32,000-34,000 daltons; and glycoprotein A3, 37,000-38,000 daltons; pH at isoelectric point (pI) 4.5-5.0. Glycoproteins A2 and A3 were electroeluted and used to prepare a monospecific antiserum that identified proteins A1, A2, and A3 in immunoblots of crude surfactant obtained from dog lung lavage. This antiserum precipitated several proteins from in vitro translated canine lung poly(A)+ mRNA; proteins of 27,000 daltons, pI 5.0, and 28,000 daltons, pI 4.8-5.0, which precisely comigrated with proteins A1 from canine surfactant. Cotranslational processing of the primary translation products by canine pancreatic microsomal membranes resulted in larger proteins of 31,000-34,000 daltons, pI 4.8-5.0. Treatment of these processed forms of glycoprotein A with endoglycosidase F, to remove N-linked carbohydrate, resulted in proteins of 27,000-28,000 daltons which precisely comigrated with surfactant protein A1. These observations demonstrate that the polypeptide precursors to the glycoproteins A complex are extensively modified by addition of asparagine N-linked complex carbohydrate and are subsequently secreted as glycoproteins A2 and A3.     

The rate of removal of pyrimidine dimers in quiescent cultures of normal human and xeroderma pigmentosum cells

The rate of removal of pyrimidine dimers from DNA of UV (254 nm)-irradiated (1 J/m2) normal and xeroderma pigmentosum (XP) cells maintained in culture as nondividing populations was determined. Several normal and XP strains from complementation groups A, C and D were studied. The excision rates and survival ability of nondividing cells were examined to determine if an abnormal sensitivity was associated with a decreased rate of dimer excision. The results show that all normal strains studied excise pyrimidine dimers at the same rate, with the rate curve characterized by two components. All 'excision-deficient' XP strains excise dimers at a slower-than-normal rate, with the rate curves also characterized by two components. The rate constants for the first components of all of the XP strains (group A, C and D) are the same, one tenth of the normal rate constant, except for XP8LO (group A). XP8LO has a first-component rate constant similar to that of normal strains and a second component rate constant similar to that of other group A strains (XP12BE, XP25RO). Thus, the slower rate of dimer excision in XP8LO is due to a defect in the mechanism responsible for the second component of the excision-rate curve. In general, an abnormal sensitivity of nondividing cells to UV is associated with a reduced dimer-excision rate. A notable exception to this is the group C strain XP1BE which has an initial repair rate similar to that of group A XP12BE but is considerably more resistant when survival is measured.     

Studies towards the development of chemically synthesized non-radioactive biotinylated nucleic acid hybridization probes.

Non-radioactive nucleic acid hybridization probes have been constructed in which the reporter group is long chain biotin chemically linked to a basic macromolecule (histone H1, cytochrome C or polyethyleneimine). The modified basic macromolecule which carries many biotin residues can, in turn, be covalently linked to nucleic acids (DNA) via the bifunctional cross-linking reagents, glutaraldehyde, 1,2,7,8-diepoxyoctane, bis (succinimidyl) suberate or bis (sulfonosuccinimidyl) suberate. This provides a very sensitive probe by which as little as between 10-50fg of target DNA can be visualized using dot-blot hybridization procedures in conjunction with avidin or streptavidin enzyme conjugates.     

Molecular cloning of the F8 fimbrial antigen from Escherichia coli

Abstract The genetic determinant coding for the P-specific F8 fimbriae was cloned from the chromosome of the Escherichia coli wild-type strain 2980 (O18:K5:H5:F1C, F8). The F8 determinant was further subcloned into the Pst I site of pBR322 and a restriction map was established. In a Southern hybridization experiment identity between the chromosomally encoded F8 determinant of 2980 and its cloned counterpart was demonstrated. The cloned F8 fimbriae and those of the wild type strain consist of a protein subunit of nearly 20 kDa. F8 fimbriated strains were agglutinated by an F8 polyclonal antiserum, caused mannose-resistant hemagglutination and attached to human uroepithelial cells. The cloned F8 determinant was well expressed in a variety of host strains.     

Aspects of the Drought Tolerance in Creosotebush (Larrea divaricata)

In order to understand better the physiological adaption of creosotebush (Larrea divaricata Cav.) to drought conditions, its carbohydrate and nitrogen metabolism after a 7-day desiccation period under controlled conditions were studied. Although fructose was not significantly altered in the leaves of desiccated plants, as compared to those maintained under normal moisture conditions, both glucose and sucrose were significantly reduced. Total amino acids more than doubled under moisture stress, the increase being predominantly due to proline, phenylalanine, and glutamic acid. Significant increases also occurred in alanine, arginine, histidine, isoleucine, and valine. Increases or decreases in other amino acids were not significant. These stress-induced changes in certain amino acids are considered in relationship to protein hydrolysis, to accumulation of nitrogen degradation products translocated from the roots, and to the possible function of specific amino acids (e.g., proline) in NH₃⁺ storage.