Molecular cloning of cDNA coding for human preprourokinase

A cDNA library was constructed in pBR322 from 18S to 20S mRNA that was extracted from human kidney cells, fractionated on oligo(dT)-cellulose column and sucrose-density gradient, and confirmed for urokinase production in Xenopus laevis oocytes. The Escherichia coli RR1 transformants were hybridized to synthetic oligonucleotide probe prepared according to the known amino acid sequence, Glu 73 to Glu 77 of human urinary urokinase chain B. The entire cloned cDNA covers a 2250-bp region, wherein the 1293-bp sequence codes for preprourokinase consisting of 431 amino acids, with the first 20 residues being a signal peptide. The 5'-untranslated region is at least 80 bp long and the 3'-untranslated region is longer than 850 bp.     

High density of transmembrane glycoproteins on the flagellar surface of boar sperm cells

Membrane halves of boar sperm flagella were produced by freeze-fracture and labeled in situ with concanavalin A and wheat germ agglutinin; the lectins were visualized with protein-gold complexes. Concanavalin A and wheat germ agglutinin binding sites partition with both protoplasmic and exoplasmic halves of the membrane. A high density of lectin marking was found on protoplasmic membrane halves; we conclude that the label corresponds to transmembrane glycoproteins that, on freeze-fracture, are dragged across the outer (exoplasmic) half of the phospholipid bilayer. Our demonstration of numerous transmembrane proteins in sperm flagella offers the structural setting for previous models on flagellar surface motility that postulate accessibility of motile membrane components to the submembranous cytoskeleton.     

Effect of temperature on drought resistance and growth of cotton plants

In cotton plants ( Gossypium hirsutum L. cv. B.J.A.) the temperature of the roots affected both root and shoot growth, as did the temperature of the shoot. Drought resistance increased when the temperature imposed on roots (27°C) was lower than that imposed on shoots (17°C); the result was a decrease in both transpiration and flow of root sap. Stomatal characteristics as measured by density, index and resistance, depended only on shoot temperature. Differences in drought resistance, depended only on shoot temperature. Differences in drought resistance seem to be a result of changes in transpiration flow modulated by the amount of absorbed water.     

A rapid posttranslational myristylation of a 68-kD protein in D. discoideum

Cells incubated with [3H]myristate were shown to rapidly and specifically acylate a 68-kD protein, p68, in a developmentally-regulated manner. The fatty acid incorporated into p68 was identified as myristate, and is linked to the protein via an amide bond, apparently to an NH2-terminal glycine. The acylation of p68 in D. discoideum displays some unusual properties. Unexpectedly, myristylation of p68 is a posttranslational event and occurs in the presence of inhibitors of protein synthesis. Another unusual finding was that although p68 is a stable protein, the acyl moiety is removed with a half time of approximately 15 min.     

Through-bond electron-transfer interaction in proteins

A model for the through-bond electronic interaction between electron donor and acceptor in proteins is developed. We use a one-electron Hamiltonian, write the Dyson's equation in site representation and solve it by using a Green's function formalism with some renormalization ideas. An expression for Tab which describes the exponential decay with distance bond per bond is obtained. Covalent, non-covalent and convergent pathways are considered and no periodic approximation is needed.     

Serine/threonine protein phosphatases in Dictyostelium discoideum: no evidence for type I activity.

Extracts from Dictyostelium discoideum contain type 2A and 2C serine/threonine-specific protein phosphatases with properties very similar to those from mammals according to their sensitivity to okadaic acid and to their dependence for divalent cations. In contrast, no type 1 protein phosphatase is found at any time of development, neither in the cytosolic nor in the particulate fraction, using glycogen phosphorylase a, casein, histone or the non-proteinous 4-Methylumbelliferyl phosphate as substrates. Both type 2A and 2C protein phosphatase activities remain constant throughout the development cycle.