The 3-D crystal structure of interleukin-1 beta (IL-1 beta) has been used to define its receptor binding surface by mutational analysis. The surface of IL-1 beta was probed by site-directed mutagenesis. A total of 27 different IL-1 beta muteins were constructed, purified and analyzed. Receptor binding measurements on mouse and human cell lines were performed to identify receptor affinities. IL-1 beta muteins with modified receptor affinity were evaluated for structural integrity by CD spectroscopy or X-ray crystallography. Changes in six surface loops, as well as in the C- and N-termini, yielded muteins with lower binding affinities. Two muteins with intact binding affinities showed 10- to 100-fold reduced biological activity. The surface region involved in receptor binding constitutes a discontinuous area of approximately 1000 A2 formed by discontinuous polypeptide chain stretches. Based on these results, a subdivision into two distinct local areas is proposed. Differences in receptor binding affinities for human and mouse receptors have been observed for some muteins, but not for wild-type IL-1 beta. This is the first time a difference in binding affinity of IL-1 beta muteins to human and mouse receptors has been demonstrated.

In the search for aldosterone antagonists with an optimal activity profile, twelve 9cc,ll-epoxy-steroids were prepared and compared with their 9a, llcc-unsubstituted analogues in terms of steroid receptor binding in vitro and electrolyte excretion in vivo. Substitution of the parent structures by an epoxy group at positions 9a,ll resulted in marginal effects on mineralocorticoid receptor binding and electrolyte excretion, but greatly reduced androgen and gestagen receptor binding. This finding is reflected in the largely lacking unwanted anti-androgenic and gestagenic side effects in animal models of the three most interesting 9cc,1l-epoxy-spirolactones 4(CGP 33 033), lS(CGP 29245), and 25(CGP 30083).

It is shown that rifampicin, and especially the related antibiotic 2',6'-dimethyl-N(4')-benzyl-N(4')-[desmethylirifampicin (DMB-rifampicin) can inhibit focus formation by Moloney sarcoma virus on BALB/3T3 tissue cultures. At 10 ug/ml DMB-rifampicin totally inhibits focus formation while reducing virus replication by at least a factor of fifty and cell proliferation by only a factor of three. These observations, taken together with those of others, suggest a role for an RNA-dependent DNA polymerase and the gene for its synthesis both in normal cell processes and in the transformation process.

One of the most potent inhibitors of RNA-dependent DNA polymerase activity so far described (rifazacyclo-16) was not correspondingly as active in focus inhibition. This discrepancy was thought to be due to the inability of the drug to penetrate the cell membrane. It has been found that a very low level of amphotericin B allows this drug, as well as the previously described 2',6'-

A reverse transcriptase activity, extracted from virus-transformed cells, is activated by very low concentrations of nonionic detergents. These same detergents also significantly reduce the effectiveness of certain rifamycin derivatives as inhibitors of the polymerase activity when the detergents are present at micelle-forming concentrations.