Dynamic Expansion and Functional Evolutionary Profiles of Plant Conservative Gene Family SBP-Box in Twenty Two Flowering Plants and the Origin of miR156

Conservative gene families in plants, which are closely related to innovations in flowering plants, have long and complex evolutionary histories. Here, we used the SQUAMOSA promoter-binding protein (SBP-box) gene family as an example to study conservative gene families in flowering plants. In total, 11 groups, including nine angiosperm-conservative groups and two monocot- and eudicot-specific groups, were identified. Among the nine angiosperm-conservative groups, four are conserved in all land plants and the remaining five are angiosperm-specific. The five angiosperm-specific groups exhibit structural and functional diversity and evolved together, along with the evolution of flowering plants. The expansion of SBP genes was affected by miR156, and the miR156-regulated SBP genes tend to retain more copies. Our results reflect the dynamic evolutionary process of the different groups, with the identification of two genetic lines via synteny analyses. In addition, miR156 showed a close evolutionary relationship with SBP genes, suggesting that it may originate from face-to-face tandem duplication of SBP genes. SBP genes without an miR156 binding locus are usually functionally conservative or housekeeping like, belonging to the terrestrial-conservative group. In contrast, SBP genes with miR156 binding sites are selected by angiosperms to regulate more complex physiological processes.

Estimation of a stronger heparin binding locus in fibronectin domain III14 using thermodynamics and molecular dynamics

Binding Thermodynamics of FHIP I and FHIP II with heparin.

Kinetics of Inward-Rectifier K+ Channel Block by Quaternary Alkylammonium Ions

We examined block of two inward-rectifier K+ channels, IRK1 and ROMK1, by a series of intracellular symmetric quaternary alkylammonium ions (QAs) whose side chains contain one to five methylene groups. As shown previously, the ROMK1 channels bind larger QAs with higher affinity. In contrast, the IRK1 channels strongly select TEA over smaller or larger QAs. This remarkable difference in QA selectivity between the two channels results primarily from differing QA unbinding kinetics. The apparent rate constant for binding (kon) of all examined QAs is significantly smaller than expected for a diffusion-limited process. Furthermore, a large (∼30-fold) drop in kon occurs when the number of methylene groups in QAs increases from three to four. These observations argue that between the intracellular solution and the QA-binding locus, there exists a constricted pathway, whose dimension (∼9 Å) is comparable to that of a K+ ion with a single H2O shell.

An examination of the utility of photogenerated reagents by using α-chymotrypsin

As a test of the labelling characteristics of photogenerated reagents, an aryl azide was photolysed in the aromatic-binding locus of a protein of known tertiary structure. The acyl-enzyme derived from the reaction of α-chymotrypsin with the p-nitrophenyl ester of p-azido[14C]cinnamate was isolated and photolysed. About 60% of the acyl group is covalently bound to the protein after photolysis and deacylation, and labelled enzyme is inactive. The covalently attached label is localized in the C chain of chymotrypsin, and there are firm indications that the major labelled tryptic fragment of the C chain is that which constitutes the aromatic-binding locus of the enzyme. The high degree of labelling of that portion of the protein molecule predicted on the basis of the known chemistry and structure of α-chymotrypsin, provides gratifying confirmation of the utility of the photo-labelling method.

AN IMMUNOFLUORESCENT TECHNIQUE FOR OBSERVING THE BINDING OF CONCANAVALIN A TO FROZEN TISSUE SECTIONS

An indirect fluorescent antibody technique has been developed to observe the binding locus of concanavalin A (CON A) to specific structures in frozen tissue sections. The technique was developed using frontal sections of the embryonic rat head with particular attention focused on the secondary palate. The binding of CON A appeared to be mainly extracellular with the most intense fluorescence observed in basement lamina and cartilaginous structures. CON A binding was highly specific in that it was eliminated in the presence of competing sugars such as α-methyl mannoside. This relatively quick and simple technique should allow the observation of developmental or pathologic changes in CON A binding to frozen tissue sections from a variety of sources.