The chain growth rate of T4 lysozyme in vitro

Kinetics of repeat propagation in the microgene polymerization reaction

Repetitive DNA is a periodic copolymer with the intrinsic property of exponential propagation to longer repeats. Microgene polymerization reaction (MPR) is a model system in which a short nonrepetitive homo-duplex DNA evolves to multiple repetitive products during heat-cool cycles. The mechanism underlying this process involves staggered annealing of complementary DNA strands of variable lengths and polymerase-mediated filling-in of the generated overhangs. MPR is considered here as a process sharing common features with two polymerization types, chain-growth and step-growth, and significant distinctions from both types were highlighted. The involved reaction stages were formulated and a kinetic model was derived and tested experimentally. The model can quantitatively explain MPR propagation and be used as a good approximation for this phenomenon.

Efficacy of translation in the rickettsia Coxiella burnetii

The addition of coliphage Q beta ribonucleic acid to a cell-free translation system obtained from Coxiella burnetii cells caused the formation of monosomes and disomes from ribosomal subunits and resulted in synthesis of viral coat protein. Rickettsial ribosomes and associated translation factors functioned together, with fidelity, efficiency, and a specificity similar to those of free-living gram-negative bacteria.

Protein folding

This review describes recent advances in studies on the stabilities of the three-dimensional structures of proteins and on the processes leading to the formation of these structures. The term ‘protein folding’ will be used here to denote the process of the conversion of an open polypeptide chain into the unique three-dimensional conformation of the native protein. Experimental and theoretical aspects of protein folding have been reviewed by anfinsen & Scheraga (1975). In the present article, we emphasize advances made since the writing of that review, together with a brief summary of the background of recent studies.

Inhibition of RNA-directed DNA polymerase by aurintricarboxylic acid

Commercial-grade aurintricarboxylic acid (ATA) inhibits poly(A), poly(C) and viral RNA-directed DNA synthesis by detergent-disrupted virions of Moloney murine leukemia virus. Paper chromatography of crude ATA yields two active components, which appear to behave identically, and at least two inactive components. The concentration of ATA needed to inhibit polymerase activity is proportional to the concentration of viral protein. The inhibition is neither attributable to contaminating heavy metal ions in the ATA preparation nor to chelation by ATA of Mn2+ or Zn2+, the necessary co-factors. Inhibition of the polymerase reaction by ATA greatly increases the Km for the primer [oligo(T)/oligo(dG)], while it only slightly lowers the Vmax and does not affect the Km's for the template [poly(A)/poly(C)] or the substrate (TTP/dGTP). Thus, ATA seems to reduce specifically the affinity of the polymerase for the DNA primer molecule.

Aurintricarboxylic acid, a preferential inhibitor of initiation of protein synthesis

The effect of aurintricarboxylic acid (ATA) was tested on various aspects of protein synthesis directed by the natural messenger ribonucleic acid (RNA) isolated from R17 RNA bacteriophage. The effects of various levels of ATA (up to 1,000 mum) were tested on overall protein synthesis as well as on binding of messenger RNA and fmet-transfer RNA to ribosomes and on the addition of the 50S ribosome to the 30S ribosome initiation complex. All of the reactions tested could be inhibited by ATA, and none of the tested steps was found to be uniquely sensitive to it. However, the total initiation steps were more sensitive to this chemical than the elongation steps; thus, under appropriate conditions this chemical can preferentially inhibit initiation while elongation of the polypeptide chain is not appreciably affected.

Inhibition of polyuridylic acid-directed protein synthesis by aurintricarboxylate in extracts of Escherichia coli

Aurintricarboxylic acid (ATA) inhibits protein synthesis directed by polyuridylic acid. All steps tested are inhibited by ATA. We conclude that inhibition of polyphenylalanine formation is an additive effect of inhibition of various steps in the protein synthetic machinery.

Aurintricarboxylic acid: inhibitor of initiation of protein synthesis

Aurintricarboxylic acid prevents the attachment of bacteriophage messenger RNA to ribosomes. As a consequence, initiation of protein synthesis in cell-free extracts prepared from Escherichia coli or rabbit reticulocytes is inhibited at concentrations of dye that do not prevent chain extension. Its properties can be distinguished from other agents that inhibit protein synthesis, including sodium fluoride, cycloheximide, and pactamycin.

The selective inhibition of protein initiation by T4 phage-induced factors

The phenomenon of selective translation of T4 template RNA by ribosomes from T4-infected cells, or factors derived therefrom, has been extended to studies on the initiation of protein synthesis. A high-salt extract derived from T4-infected ribosomes inhibits the formation of initiation complexes of MS2 and Escherichia coli template RNA with uninfected ribosomes while efficiently supporting the formation of initiation complexes with T4 template RNA. T4 factors also permit T5 template RNA to bind to E. coli ribosomes, which indicates that the T4 selective effect is not exclusive for T4 templates. Other evidence indicates that T4 factors do not alter the process of polypeptide chain elongation.