C5a is an inflammatory mediator potentially involved in a number of diseases. To help define which of its 74 residues are important for receptor binding and response triggering, changes in the amino acid sequence of C5a were introduced by site-directed mutagenesis. Synthetic C5a-encoding genes incorporating point mutations were expressed in Escherichia coli, and the mutant proteins were purified to homogeneity. Modifications of the C5a molecule causing parallel reductions in binding to polymorphonuclear leukocyte membranes and in stimulation of polymorphonuclear leukocyte locomotion (chemokinesis) suggest that carboxyl-terminal residues Lys-68, Leu-72, and Arg-74 interact with the receptor. Substitutions in the disulfide-linked core of C5a revealed involvement of Arg-40 or nearby residues, because potency losses were associated with only localized conformational changes as detected by NMR. Surprisingly, a substitution at core residue Ala-26, which did not alter C5a core structure, appeared from NMR results to reduce potency by causing a long-distance conformational change centered on residue His-15. Thus, at least three discontinuous regions of the C5a molecule appear to act in concert to achieve full potency.

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A series of 7-(1H-pyrrol-3-yl)-substituted-3,5-dihydroxyhept-6(E)- enoates (-heptanoates) 1 and 2 have been prepared and tested for inhibiti 3-hydroxy-3-methylglutaryl-coenzyme A reductase. The most potent compounds exceeded mevinolin's activity in vitro and in vivo.

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Poor expression of a synthetic gene for the inflammatory mediator, C5a, was observed in E. coli grown in rich media. Varying the media composition markedly improved expression, although C5a levels still declined rapidly at the end of log phase. Using a protease-deficient strain, C5a was recovered at stationary phase in high yield (13 mg/liter of culture). Recovery was dependent on guanidinium hydrochloride extraction to solubilize the protein and glutathione treatment to promote correct folding. Two-thirds of the C5a retained an amino-terminal methionine. Both forms of recombinant C5a had activity similar to serum-derived C5a in binding to human neutrophil receptors and inducing chemotaxis. The 700-fold improvement in yield made it feasible to obtain gram amounts of C5a and provides an efficient system for site-directed mutagenesis.

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Lactones of pyridine- and pyrimidine-substituted 3,5-dihydroxy-6-heptenoic (-heptanoic) acids 2-4 have been synthesized. Extensive exploration of structure-activity relationships led to several compounds exceeding the inhibitory activity of mevinolin (1b) on HMG-CoA reductase, both in vitro and in vivo. First clinical trials with 2i (HR 780) are in preparation.

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