ON THE COVER
Secretory vesicles containing MMP9-GFP near the plasma membrane of MCF-7 breast cancer cells. Overlay of TIRF MMP9-GFP image (green) and platinum replica TEM image (gray) of a MCF-7 cell plasma membrane sheet. Note the presence of other unlabeled membrane structures found on the MCF-7 cell membrane (e.g., actin filaments are visible all around the secretory vesicles). Image © Stephens et al., 2019. See https://doi.org/10.1085/jgp.201812299.
- PDF Icon PDF LinkTable of Contents
- PDF Icon PDF LinkEditorial Board
Squire and Luther consider new evidence for a simple lattice structure in mammalian skeletal muscle.
Rudnick highlights a kinetic analysis of a bacterial Nramp transporter that focuses on how H+ gradients are coupled to metal transport.
Twomey et al. examine recent structural and functional data that have provided insight into AMPA receptor modulation by TARPs.
KtrAB is a bacterial ion channel with a noncanonical selectivity filter. Consequently, it was assumed to be rather unselective for monovalent cations. Mikušević et al. show that in the presence of Na+, KtrAB very selectively translocates K+, which results from a high binding affinity and facilitated K+ gating.
Outer hair cell electromotility is low-pass filtered relative to the molecular conformational changes that produce nonlinear capacitance
Cochlear amplification is mediated by the outer hair cell of the organ of Corti. Santos-Sacchi et al. reveal that the cell possesses a voltage-dependent motile frequency response that differs from that of its voltage sensor/effector, the electromotile protein prestin, implying variable coupling between the two.
Spatiotemporal organization and protein dynamics involved in regulated exocytosis of MMP-9 in breast cancer cells
This paper describes the dynamics of proteins and lipids during exocytosis of MMP-9 from cancer cells in real time using fluorescence microscopy. Stephens et al. find that core exocytic proteins, accessory proteins, and lipids are involved at sites of secretory vesicle fusion.
Ma et al. studied the 3-D arrangement of thick filaments in skeletal muscle by x-ray diffraction and electron microscopy and found a correlation between thick filament lattice type (simple or superlattice) and fiber type (fast/slow). This suggests that lattice organization contributes to muscle functional properties.
Unique structural features in an Nramp metal transporter impart substrate-specific proton cotransport and a kinetic bias to favor import
An Nramp transition metal transporter performs metal uniport, proton uniport, and proton–metal cotransport. Transmembrane voltage and pH gradients govern the rates of these processes, largely through a conserved salt-bridge network in the transmembrane scaffold of the transporter’s LeuT fold.