Sigler, Paul

TFIIA and TFIIB are two basal transcription factors that are involved in the nucleation stages of the preinitiation complex by binding to the TBP-TATA box complex. Crystal structures of the ternary complex TFIIA-TBP-TATA box have been determined by the groups of Paul Sigler, Yale University, and Timothy Richmond, ETH, Zurich, and that of the TFIIB-TBP-TATA box by Stephen Burley and collaborators. The TBP-DNA interactions and the distortions of the DNA structure are essentially the same in these ternary complexes as in the binary TBP-TATA complex. 

The structure of the apy-holocomplex of transducin from bovine rod outer segments of the retina, which was solved in Paul Sigler s laboratory, is presented in Plate 7. 

The three-dimensional structures of GTPyS-Gj-al of Coleman a of the trans-ducin a-GDP-AlF4 complex by Sondek et and Gj -a hum Paul Sigler s laboratory, ref. 84, show how the crucial Arg-residue contacts the y-phosphate of GTP directly. Thus, the presence or absence of the y-phosphate in the guanine nucleotide defines the active or inactive state of a G a-subunit. 

Fig. 5.4 A ribbon model of the G p-subunit, which has WD (Tip-Asp) repeats and forms p-propellers. This structure is like a scaffold, presenting a surface to which other proteins can bind. (The structure was solved in Paul Sigler s laboratory s and is reproduced with permission of the authors and Nature.)...

A phosphorylated serine in the receptor serves as a structural marker for the recc nition of arrestin. Arrestin has practically no affinity for the unphosphorylated receptor, but the phosphorylated receptor, rhodopsin, binds with a Kj) in the order of about 50 nM. Three-dimoisional structures of arrestin fi om bovine rod outer segments have been reported at 3.3 and 2.8 A resolution. We show the more recent, higher-resolution structure firom Paul Sigler s laboratory (Fig. 5.6). 5... 

Thanks mainly to the efforts of the Strasbourg group of D. Moras and Pierre Chambon, and Paul Sigler s laboratory at Yale University, three-dimensional structural information is now available in the case of heterodimeric RXR/TR and RXR/RAR DBDs bound to direct DNA repeats (DR4 and DR5), respectively (Plate 24 and Fig. 11.11). This is one of the still rather rare cases where one can profitably explain, on a molecular basis, the interactions of a receptor with the ligand and with target genes. 

Paul B. Sigler (53), Department of Molecular Biophysics and Biochembtry, Howard Hughes Medical Institute, Yale University, New Haven, Connecticut 06510... 

P. B., 1997, Nature 388, 741—730. Molecular graphics courtesy of Paul B. Sigler, Yale University.)... 

In contrast to proteins and as noticed several years ago by Paul Sigler (1), secondary structure is defined by H-bonds between side chains in RNA and not by H-... 

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