An expanding universe of small proteins

Historically, small proteins (sproteins) of less than 50 amino acids, in their final processed forms or genetically encoded as such, have been understudied. However, both serendipity and more recent focused efforts have led to the identification of a number of new sproteins in both Gram-negative and Gram-positive bacteria. Increasing evidence demonstrates that sproteins participate in a wide array of cellular processes and exhibit great diversity in their mechanisms of action, yet general principles of sprotein function are emerging. This review highlights examples of sproteins that participate in cell signaling, act as antibiotics and toxins, and serve as structural proteins. We also describe roles for sproteins in detecting and altering membrane features, acting as chaperones, and regulating the functions of larger proteins.     

IgM-mediated enhancement of in vivo anti-sheep erythrocyte antibody responses: isotype analysis of the enhanced responses

The direct splenic anti-sheep erythrocyte (anti-SRBC) responses as well as the serum IgG1, IgG2a, IgG2b, and IgG3 anti-SRBC responses of CBA/CaJ mice were monitored 4-35 days after immunization with: (1) a suboptimal dose of SRBC, (2) a suboptimal dose of SRBC plus monoclonal IgM anti-SRBC, or (3) a high dose of SRBC. The direct plaque-forming cell (PFC) responses of mice in treatment group 2 were significantly higher than those in group 1 but similar to the responses in group 3. The serum anti-SRBC antibody responses of all IgG subclasses were significantly enhanced by IgM anti-SRBC and were generally even higher than the responses obtained with high doses of SRBC. The relative proportions of each serum IgG subclass were similar in all three groups. These data suggest that the enhancement of suboptimal anti-SRBC antibody responses by IgM anti-SRBC extends through IgM and all of the IgG subclasses and, further, that the isotype profile in antibody-enhanced responses is similar to that obtained with high doses of SRBC.     

Synthesis of polymerized thin films for immobilized ligand display in proteomic analysis

We describe a new material for the display of biomolecular ligands for use in proteomic analysis. We report here on the construction of the first functionalized polymerized diacetylene thin films (PDTFs) for use in displaying immobilized ligands and their application in mass spectral proteomic analysis. Functionalized polymerized thin film surfaces were constructed with diacetylene-containing biotin lipid monomers designed for the capture of proteins (streptavidin) from a complex cellular lysate and detection with mass spectrometry (MS). These materials serve as a prototype for ligand-based spotted arrays amenable to high throughput screening. Functionalized PDTFs can be easily manufactured for customized microarrays and demonstrate high protein specificity and low nonspecific protein adsorption, and the resulting microarrays constructed from these materials are compatible with several different protein analysis platforms. Our results suggest that these materials have broad potential applications for use in mass spectral-based proteomic analysis.     

Distinct contributions of T1R2 and T1R3 taste receptor subunits to the detection of sweet stimuli

Animals utilize hundreds of distinct G protein-coupled receptor (GPCR)-type chemosensory receptors to detect a diverse array of chemical signals in their environment, including odors, pheromones, and tastants. However, the molecular mechanisms by which these receptors selectively interact with their cognate ligands remain poorly understood. There is growing evidence that many chemosensory receptors exist in multimeric complexes, though little is known about the relative contributions of individual subunits to receptor functions. Here, we report that each of the two subunits in the heteromeric T1R2:T1R3 sweet taste receptor binds sweet stimuli though with distinct affinities and conformational changes. Furthermore, ligand affinities for T1R3 are drastically reduced by the introduction of a single amino acid change associated with decreased sweet taste sensitivity in behaving mice. Thus, individual T1R subunits increase the receptive range of the sweet taste receptor, offering a functional mechanism for phenotypic variations in sweet taste.     

Unusual olefin formation by PhSe-F trans-elimination

A new approach to the synthesis of 2',3'-didehydro-2',3-dideoxynucleosides was described in excellent yield through unusual olefin formation by PhSe-F trans-elimination.