The helix-loop-helix (HLH) family of transcription factors comprises >200 members, which have been identified in organisms from yeast to man (reviewed in Littlewood and Evan, 1995; Massari and Murre, 2000). In metazoa, HLH proteins function in the coordinate regulation of gene expression, orchestrating cell cycle control, cell lineage commitment and cell differentiation. An essential role has b...

Fifteen triterpenoid saponins were isolated from the berries of Hedera colchica and their structures established on the basis of chemical and spectroscopic evidence. Among them, two are new compounds: coichiside A (3) and colchiside B (15) and four are described for the first time in the berries of Hedera colchica (compounds 1, 8, 9 and 11).

An information theoretic approach is used to examine the magnitude and origin of associations among amino acid sites in the basic helix-loop-helix (bHLH) family of transcription factors. Entropy and mutual information values are used to summarize the variability and covariability of amino acids comprising the bHLH domain for 242 sequences. When these quantitative measures are integrated with cr...

Robust methods to detect DNA-binding proteins from structures of unknown function are important for structural biology. This paper describes a method for identifying such proteins that (i) have a solvent accessible structural motif necessary for DNA-binding and (ii) a positive electrostatic potential in the region of the binding region. We focus on three structural motifs: helix-turn-helix (HTH...

HISTORY ......... .............................................................................................................. 97 A Thermodynamic Model of a-Helix Formation ....................................................... 97 Statistical Mechanical Models of a-Helix Formation................................................ 98 Tests of Helix-Coil Theory and Values for Parameters ...........

There is much activity directed at quantifying the contribution of specific interactions to the stabilization of protein structure. The paper by Myers et al. (1) in this issue of the Proceedings addresses a central and much studied issue: The experimental measure of the intrinsic a-helix forming propensities of the amino acids. What is an intrinsic a-helix forming propensity? The idea that the ...

OGlcNAcylation and phosphorylation are the major competing intracellular post-translational modifications of serine and threonine residues. The structural effects of both post-translational modifications on serine and threonine were examined within Baldwin model α-helical peptides (Ac-AKAAAAKAAAAKAAGY-NH2 or Ac-YGAKAAAAKAAAAKAA-NH2). At the N-terminus of an α-helix, both phosphorylation and OGl...