Charles L. Lawson

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The crystal structure of the trp repressor/operator complex shows an extensive contact surface, including 24 direct and 6 solvent-mediated hydrogen bonds to the phosphate groups of the DNA. There are no direct hydrogen bonds or non-polar contacts to the bases that can explain the repressor's specificity for the operator sequence. Rather, the sequence seems(More)
The crystal structure of the Escherichia coli trp repressor has been solved to atomic resolution. The dimeric protein has a remarkable subunit interface in which five of each subunit's six helices are interlinked. The binding of L-tryptophan activates the aporepressor indirectly by fixing the orientation of the second helix of the helix-turn-helix motif and(More)
Comparison of the crystal structure of inactive unliganded trp aporepressor with that of trp repressor shows that binding tryptophan activates the dimer a thousandfold by moving two symmetrically-disposed flexible bihelical motifs. These flexible 'DNA-reading heads' flank a highly inflexible core domain formed by an unusual arrangement of interlocking(More)
I recently had occasion to extend a derivative-computation package I had written in 1971 to add the capability of dealing with a function defined implicitly. This led me to see the duality between Taylor series reversion and the chain rule of differentiation of a composite function. I was also struck with the compactness with which these algorithms could be(More)
The trp repressor is a small dimeric regulatory protein which controls the expression of three operons in Escherichia coli. The inactive aporepressor protein must bind two molecules of L-tryptophan to form the active repressor. If desamino analogues of L-tryptophan such as indole propionate (IPA) are substituted for L-tryptophan, an inactive pseudorepressor(More)
This paper is one of three to be presented at a joint meeting of SIGNUM and the ANSI X3J3 Fortran Committee October 18, 1978, for the purpose of communicating suggestions arising in the mathematical software community to the X3J3 Committee. A summary is given of language problem areas and possible solutions that have been discussed by the IFIP Working Group(More)
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