On the origins of esterases

Comparisons among the primary sequences of five cloned eukaryotic esterases reveal two distinct lineages, neither bearing any significant overall sequence similarity to the functionally related serine protease multigene family. We have not eliminated the possibility that the esterases may have residual conformational similarities to the serine proteases. However, our profile analysis and analyses of the predicted conformations of the esterases reveal little similarity to the serine proteases. Four of the esterase proteins share 27%-53% overall sequence similarity and evidence of a catalytic mechanism involving the same Arg- Asp-Ser or His-Asp-Ser charge relay. We propose that these four esterases, three of them cholinesterases, form part of a multigene family essentially separate from the serine proteases.      

Excluded volume effects on the rate of renaturation of DNA

The rate of renaturation of T2 DNA hits been investigated by using complementary DNA strands of different length. The length of the shorter strand ranged from 0.02 to 1.0 times the length of the longer strand. An excluded volume theory is developed to include this type of reaction as well as the DNA–RNA hybridization reaction. Experimental and theoretical rates of renaturation of DNA are found to be in agreement. For the cases studied, the rate was never greater than twice that observed for short strands of the same length renaturing with themselves. The products of renaturation reactions are also considered.     

Length dependence of the kinetic complexity of mouse satellite DNA

Treatment of renatured mouse satellite DNA with the single stranded DNA specific endonuclease Sl leads to the isolation, with no losses, of regions of length, L ≤ 56±28, from molecules containing several such regions. The rate of renaturation is observed to be an unusual function of length, extrapolating to an apparent complexity, N ≤ 36±9. The results are consistent with a model of tandem, spaced, repetitions where multiple nucleations may occur between two strands containing the complementary repetition units.     

Assembly of splicing complexes on exon 11 of the human insulin receptor gene does not correlate with splicing efficiency in-vitro

Background  

Incorporation of exon 11 of the insulin receptor gene is both developmentally and hormonally-regulated. Previously, we have shown the presence of enhancer and silencer elements that modulate the incorporation of the small 36-nucleotide exon. In this study, we investigated the role of inherent splice site strength in the alternative splicing decision and whether recognition of the splice sites is the major determinant of exon incorporation.     

Acceleration of DNA renaturation rates

The rate of renaturation of DNA may be increased by altering the effective solvent volume available for DNA in solution. Accelerations are demonstrated when neutral and anionic dextran polymers are used to exclude volume in DNA solutions. The logarithm of the DNA renaturation rate constant is shown to be proportional to the concentration of dextran polymer and to be proportional to the intrinsic viscosity of a series of dextran polymers of identical chemical composition. A theory is proposed to account for these results.