ABSTRACT
The formation of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes between opposing membranes is an essential prerequisite for fusion between vesicles and their target compartments. The composition and length of a SNARE's transmembrane domain (TMD) is also an indicator for their steady-state distribution in cells. The evolutionary conservation of the SNARE TMD, together with the strict requirement of this feature for membrane fusion in biochemical studies, implies that the TMD represents an essential protein module. Paradoxically, we find that for several essential ER- and Golgi-localized SNAREs, a TMD is unnecessary. Moreover, in the absence of a covalent membrane tether, such SNAREs can still support ER-Golgi vesicle transport and recapitulate established genetic interactions. Transport anomalies appear to be restricted to retrograde trafficking, but these defects are overcome by the attachment of a C-terminal lipid anchor to the SNARE. We conclude that the TMD functions principally to support the recycling of Qb-, Qc-, and R-SNAREs and, in so doing, retrograde transport.
Subject(s)
SNARE Proteins/metabolism , SNARE Proteins/physiology , Biological Transport , Cell Membrane/metabolism , Endoplasmic Reticulum/metabolism , Endoplasmic Reticulum/physiology , Golgi Apparatus/metabolism , Golgi Apparatus/physiology , Membrane Fusion/physiology , Membrane Proteins/metabolism , Protein Binding , Protein Domains , Protein Transport , Qa-SNARE Proteins/metabolism , Qb-SNARE Proteins/metabolism , Qc-SNARE Proteins/metabolism , R-SNARE Proteins/metabolism , Saccharomyces cerevisiae Proteins/metabolism , Vesicular Transport Proteins/metabolismABSTRACT
Antiferromagnets are hard to control by external magnetic fields because of the alternating directions of magnetic moments on individual atoms and the resulting zero net magnetization. However, relativistic quantum mechanics allows for generating current-induced internal fields whose sign alternates with the periodicity of the antiferromagnetic lattice. Using these fields, which couple strongly to the antiferromagnetic order, we demonstrate room-temperature electrical switching between stable configurations in antiferromagnetic CuMnAs thin-film devices by applied current with magnitudes of order 10(6) ampere per square centimeter. Electrical writing is combined in our solid-state memory with electrical readout and the stored magnetic state is insensitive to and produces no external magnetic field perturbations, which illustrates the unique merits of antiferromagnets for spintronics.
