Local deformation studies of chain molecules: differential conditions for changes of dihedral angles

New first and second-order differential equations for changes of dihedral angles characterizing local deformations of chain molecules with fixed bond lengths and bond angles are derived. Two methods for integrating the differential relations are given. The proposed method is used to generate a path of locally deformed conformations around a β-turn region of a small protein, bovine pancreatic trypsin inhibitor. The variable regions change their conformations by more than 3 Å root-mean-square distance value whereas the fixed regions stay within 0.02 Å. Possible applications of this method are in the field of computer graphics, Monte Carlo simulations, and energy minimization calculations of chain molecules.     

The study of a French family with two duplicated C4A haplotypes

Summary The finding of two duplicated C4A haplotypes in a normal French family led to a detailed study of their C4 polymorphism. The father had an extremely rare A^*6A^*11, B^* QO haplotype inherited by all of his children and the mother had the more common A^*3A^*2, B^*QO haplotype. Two HLA identical daughters only have four C4A alleles. The father's A11 allotype expresses Ch: 1 (Chido) rather than Rg:1 (Rodgers) and represents a new Ch phenotype Ch: 1,-2,-3,-4,-5,-6. In order to clarify the genetic background in this unusual family, DNA studies of restriction fragment length polymorphisms (RFLPs) were undertake. The father's rare haplotype, which expresses two C4A allotypes, results from a long and a short C4 gene normally associated with the A^*6, B^*1 that also exhibits the BglII RFLP. As it travels in an extended MHC haplotype HLA A2, B57 (17), C2^*C, BF^*S, DR7 that is most frequently associated with A^*6, B^*1, we postulate that the short C4B has been converted in the chain region to a C4A gene which produces a C4A protein. This report of a short C4A gene is the first example in the complex polymorphism of C4.     

The rho gene product expressed in E. coli is a substrate of botulinum ADP-ribosyltransferase C3

The ras-related rho A protein expressed in E. coli, was ADP-ribosylated by botulinum ADP-ribosyltransferase C3. C3 also modified the valine-14 mutant rho protein but not the products of H-ras, R-ras, ral, ypt, and rap 1 genes. A ras-rho chimaera consisting of 60 amino acids from the amino terminus of ras fused to 133 amino acids from the carboxy terminus of rho was not modified by C3. Antibodies raised against the porcine brain cytosolic substrate of C3 cross reacted with the rho, valine-14 rho and ras-rho proteins, but not with the gene products of H-ras, R-ras, ral or rap 1. Polyclonal anti-H-ras antibodies cross reacted with H-ras but not with ral, rho, or the C3 substrate purified from porcine brain.     

Sequence of the fhuE outer-membrane receptor gene of Escherichia coli K12 and properties of mutants

The fhuE gene of Escherichia coli codes for an outer-membrane receptor protein required for the uptake of iron(III) via coprogen, ferrioxamine B and rhodotorulic acid. The amino acid sequence, deduced from the nucleotide sequence, consisted of 729 residues. The mature form, composed of 693 residues, has a calculated molecular weight of 77,453, which agrees with the molecular weight of 76,000 determined by polyacrylamide gel electrophoresis. The FhuE protein contains four regions of homology with other TonB-dependent receptors. A valine to proline exchange in the 'TonB box' abolished transport activity. Phenotypic revertants with substitutions of arginine, glutamine, or leucine at the valine position exhibited increasing iron-coprogen transport rates. Point mutations resulting in the replacement of glycine (127) in the second homology region with either alanine, aspartate, valine, asparagine or histidine exhibited decreased transport rates (listed in descending order). A truncated FhuE protein lacking 24 amino acids at the C-terminal end was exported to the periplasm but failed to be inserted into the outer membrane.     

Characterization of the caprine estrous cycle using enzyme immunoassay for the determination of whole blood progesterone concentration

Eighteen mature female dairy goats were used to determine the feasibility of enzyme immunoassay for the measurement of progesterone in this species. Both quantitative and qualitative enzyme immunoassay kits were used to measure progesterone concentration in unextracted whole blood. Progesterone profiles were similar to those previously reported using either protein-binding or radioimmunoassay as the test. A Pearson's correlation coefficient comparison of our enzyme immunoassay values with radioimmunoassay values gave a correlation coefficient of 0.95. Using the qualitative test, 100% of the samples with high progesterone concentrations had quantitative values greater than 4.00 ng/ml progesterone with a mean of 12.13 ng/ml. Estrus samples had a mean progesterone concentration of 0.70 ng/ml.     

Synthesis of eicosanoids by gamma-interferon-differentiated U937 cells

Interferons induce morphological, biochemical and functional alterations in monocyte macrophage and myeloid cell lines. We studied the effect of 3 days incubation with gamma-interferon from human buffy coats on the global synthesis of arachidonic acid metabolites by U937 cells. Interferon-induced morphologic changes including cytoplasmic and nuclear changes and the appearance of multiple lysosomal-like granules consistent with cellular differentiation were observed by electron microscopy. The labeling of phosphatidylserine, phosphatidylcholine and phosphatidylethanolamine was increased and that of phosphatidylinositol, free fatty acids as 3H-arachidonic acid and neutral lipids reduced, when interferon-treated cells were incubated with 3H-arachidonic acid. Interferon caused qualitative and quantitative changes in the synthesis of cyclooxygenase and lipoxygenase products. A23187, a calcium ionophore, and the tumor promotor, phorbol myristate acetate, greatly increased the synthesis by interferon-differentiated cells of 2 cyclooxygenase products; synthesis of lipoxygenase products was reduced. In the presence of indomethacin, 'shunting' into putative lipoxygenase products occurred. The relationship between interferon-induced morphologic and functional changes, the development of altered phospholipid and eicosanoid metabolism and the identity of these metabolites are yet to be established.     

pH Dependence of Histidine Affinity for Blood-Brain Barrier Carrier Transport Systems for Neutral and Cationic Amino Acids

The effects of pH (3.5-7.5) on the brain uptake of histidine by the blood-brain barrier (BBB) carriers for neutral and cationic amino acids were tested, in competition with unlabeled histidine, arginine, or phenylalanine, with the single-pass carotid injection technique. Cationic amino acid ( [14C]arginine) uptake was increasingly inhibited by unlabeled histidine as the pH of the injection solution decreased. In contrast, the inhibitory effect of unlabeled histidine on neutral amino acid ( [14C]phenylalanine) uptake decreased with decreasing pH. Brain uptake indices with varying histidine concentrations indicated that the neutral form of histidine inhibited phenylalanine uptake whereas the cationic form competed with arginine uptake. Since phenylalanine decreased [14C]histidine uptake at all pH values whereas arginine did not, it was concluded that the cationic form of histidine had an affinity for the cationic carrier, but was not transported by it. We propose that the saturable entry of histidine into brain is, under normal physiological circumstances, mediated solely by the carrier for neutral amino acids.     

Probing FhuA''-''PhoA fusion proteins for the study of FhuA export into the cell envelope of Escherichia coli K12

Summary The FhuA protein (formerly TonA) is located in the outer membrane of Escherichia coli K12. Fusions between fhuA and phoA genes were constructed. They determined proteins containing a truncated but still active alkaline phosphatase of constant size and a variable FhuA portion which ranged from 11%–90% of the mature FhuA protein. The fusion sites were nearly randomly distributed along the FhuA protein. The FhuA segments directed the secretion of the truncated alkaline phosphatase across the cytoplasmic membrane. The fusion proteins were proteolytically degraded up to the size of alkaline phosphatase and no longer reacted with anti-FhuA antibodies. The fusion proteins were more stable in lon and pep mutants lacking cytoplasmic protease and peptidases, respectively. The larger fusion proteins above a molecular weight of 64000 dalton were predominantly found in the outer membrane fraction. They were degraded by trypsin when cells were converted to spheroplasts so that trypsin gained access to the periplasm. In contrast, FhuA protein in the outer membrane was largely resistant to trypsin. It is concluded that the larger FhuA-PhoA fusion proteins were associated with, but not properly integrated into, the outer membrane.