PcG Proteins MSI1 and BMI1 Function Upstream of miR156 to Regulate Aerial Tuber Formation in Potato.

Polycomb Repressive Complexes (PRC1 and PRC2) regulate developmental transitions in plants. AtBMI1, a PRC1 member, represses micro RNA156 (miR156) to trigger the onset of adult phase in Arabidopsis (). miR156 overexpression (OE) reduces below-ground tuber yield, but stimulates aerial tubers in potato ( ssp ) under short-day (SD) photoperiodic conditions.

Salvaging the Thermodynamic Destabilization of Interface Histidine in Transmembrane β-Barrels.

The ability of histidine to participate in a wide range of stabilizing polar interactions preferentially populates this residue in functionally important sites of proteins. Histidine possesses an amphiphilic and electrostatic nature that is essential for amino acids residing at membrane interfaces. However, the frequency of occurrence of histidine at membrane interfaces, particularly transmembrane β-barrels, is lower than those of other aromatic residues.

Energetics of side-chain partitioning of β-signal residues in unassisted folding of a transmembrane β-barrel protein.

The free energy of water-to-interface amino acid partitioning is a major contributing factor in membrane protein folding and stability. The interface residues at the C terminus of transmembrane β-barrels form the β-signal motif required for assisted β-barrel assembly but are believed to be less important for β-barrel assembly Here, we experimentally measured the thermodynamic contribution of all 20 amino acids at the β-signal motif to the unassisted folding of the model β-barrel protein PagP. We obtained the partitioning free energy for all 20 amino acids at the lipid-facing interface (ΔΔ) and the protein-facing interface (ΔΔ) residues and found that hydrophobic amino acids are most favorably transferred to the lipid-facing interface, whereas charged and polar groups display the highest partitioning energy.