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Research reveals that mutations in a two gene locus blocks sporulation after polar septum formation in Bacillus subtilis. Results demonstrate that spoIISA and spoIISB genes encode two proteins, one of which preventing lethality of the other without affecting the activation process mediated by the sigma(sup)F transcription factor.

Researchers report the discovery of the taste receptor that responds to bitter tastes. It is associated with the G protein alpha subunit gustducin, which mediates bitter tastes.

Researchers report the discovery of 40 to 80 taste receptors that respond to bitter tastes. The T2R receptors occur only in taste receptor cells that have the G protein alpha subunit gustducin.

The T1R receptors, a family of taste-specific class C G protein-coupled receptors, mediate mammalian sweet and umami tastes. The structure-function relationships of T1R receptors remain largely unknown. In this study, we demonstrate the different functional roles of T1R extracellular and transmembrane domains in ligand recognition and G protein coupling. Similar to other family C G protein-coupled receptors, the N-terminal Venus flytrap domain of T1R2 is required for recognizing sweeteners, such as aspartame and neotame. The G protein coupling requires the transmembrane domain of T1R2. Surprisingly, the C-terminal transmembrane domain of T1R3 is required for recognizing sweetener cyclamate and sweet taste inhibitor lactisole. Because T1R3 is the common subunit in the sweet taste receptor and the umami taste receptor, we tested the interaction of lactisole and cyclamate with the umami taste receptor. Lactisole inhibits the activity of the human T1R1/T1R3 receptor, and, as predicted, blocked the umami taste of L-glutamate in human taste tests. Cyclamate does not activate the T1R1/T1R3 receptor by itself, but potentiates the receptor's response to L-glutamate. Taken together, these findings demonstrate the different functional roles of T1R3 and T1R2 and the presence of multiple ligand binding sites on the sweet taste receptor. [ABSTRACT FROM AUTHOR]

Examines the role of T1R class of taste-specific G protein-coupled receptors as heterodimeric sweet taste receptors. Identification of a related taste-specific receptors; Involvement of additional combinations of T1R in sweet taste; Analysis of T1R surface expression with epitopetagged receptors.