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Heterotrimeric G proteins integrate signals between receptors and effector proteins. We have cloned the human beta 5 subunit from a human brain cDNA library. The clone has a 1059 bp open reading frame and is highly homologous to the murine clone. In contrast to the brain specific mouse beta 5, northern analysis showed it to be expressed in multiple tissues.

Certain ␤-subunits exert profound effects on the kinetics of voltage-gated (K v ) potassium channel inactivation through an interaction between the amino-terminal "inactivation domain" of the ␤-subunit and a "receptor" located at or near the cytoplasmic mouth of the channel pore. Here we used a bacterial random peptide library to examine the structural requirements for this interaction. To identify peptides that bind K v 1.1 we screened the library against a synthetic peptide corresponding to the predicted S4-S5 cytoplasmic loop of the K v 1.1 ␣-subunit (residues 313-328). Among the highest affinity interactors were peptides with significant homology to the amino terminus of K v ␤1. We performed a second screen using a peptide from the amino terminus of K v ␤1 (residues 2-31) as "bait" and identified peptide sequences with significant homology to the S4-S5 loop of K v 1.1.

We have used transmitted polarized light microscopy to examine the fluid contents of silk glands taken from Bombyx mori silkworms and Nephila clavipes orb-weaving spiders. In the absence of shear, the secretions are optically isotropic. As the concentration is allowed to increase by evaporation, microstructures typical of the nematic liquid crystalline state are observed. Thus it appears that naturally spun silk becomes liquid crystalline en route to solidifying into fiber - which is advantageous to introducing and retaining global molecular alignment. This will facilitate the formation of strong, stiff fibers without the need for a significant post-spinning draw. We have also found that natural silk does not exhibit the defects in molecular alignment that are typical of synthetic polymer fibers spun from liquid crystalline solutions or melts.