Structure and electrostatic property of cytoplasmic domain of ZntB transporter

ZntB is the distant homolog of CorA Mg²⁺ transporter within the metal ion transporter superfamily. It was early reported that the ZntB from Salmonella typhimurium facilitated efflux of Zn²⁺ and Cd²⁺, but not Mg²⁺. Here, we report the 1.90 Å crystal structure of the intracellular domain of ZntB from Vibrio parahemolyticus. The domain forms a funnel-shaped homopentamer that is similar to the full-length CorA from Thermatoga maritima, but differs from two previously reported dimeric structures of truncated CorA intracellular domains. However, no Zn²⁺ or Cd²⁺ binding sites were identified in the high-resolution structure. Instead, 25 well-defined Cl⁻ ions were observed and some of these binding sites are highly conserved within the ZntB family. Continuum electrostatics calculations suggest that the central pore of the funnel is highly attractive for cations, especially divalents. The presence of the bound Cl⁻ ions increases the stability of cations along the pore suggesting they could be important in enhancing cation transport.     

The Iberian record of the puma-like cat Puma pardoides (Owen, 1846) (Carnivora,Felidae)

Fossil puma-like cats (Puma pardoides) are recorded from several Late Pliocene to Early Pleistocene Eurasian localities, but the interpretation of the phylogenetic relationships between them and the extant puma (Puma concolor) remains controversial. In the past, extinct puma-like cats have been classified into several genera and species, and a close relationship with both pumas (Puma concolor) and snow leopards (Uncia uncia) has been suggested. Here, we describe the fossil remains of puma-like cats from the Iberian Peninsula. These remains (from the localities of La Puebla de Valverde, Cueva Victoria and Vallparadís) cover the whole known chronological distribution of this species in Eurasia. Although there are dentognathic similarities with U. uncia, the Iberian remains of P. pardoides most closely resemble the extant P. concolor. It is concluded that P. pardoides is closely related to living pumas, which supports a likely Eurasian origin of the puma lineage.     

Adhesion energy of receptor-mediated interaction measured by elastic deformation

We investigated the role of receptor binding affinity in surface adhesion. A sensitive technique was developed to measure the surface energy of receptor-mediated adhesion. The experimental system involved a functionalized elastic agarose bead resting on a functionalized glass coverslip. Attractive intersurface forces pulled the two surfaces together, deforming the bead to produce an enlarged contact area. The Johnson-Kendall-Roberts (JKR) model was used to relate the surface energy of the interaction to the elasticity of the bead and the area of contact. The surface energies for different combinations of modified surfaces in solution were obtained from reflection interference contrast microscopy (RICM) measurements of the contact area formed by the bead and the coverslip. Studies with surfaces functionalized with ligand-receptor pairs showed that the relationship between surface energy and the association constant of the ligand binding has two regimes. At low binding affinity, surface energy increased linearly with the association constant, while surface energy increased logarithmically with the association constant in the high affinity regime.