The twin-arginine translocase (Tat) carries out the remarkable process of translocating fully folded proteins across the cytoplasmic membrane of prokaryotes and the thylakoid membrane of plant chloroplasts. Tat is required for bacterial pathogenesis and for photosynthesis in plants. TatA, the protein-translocating element of the Tat system, is a small transmembrane protein that assembles into r...

In Gram-negative bacteria, lipid modification of proteins is catalysed in a three-step pathway. Apolipoprotein N-acyl transferase (Lnt) catalyses the third step in this pathway, whereby it transfers an acyl chain from a phospholipid to the amine group of the N-terminal cysteine residue of the apolipoprotein. Here, we report the 2.6-Å crystal structure of Escherichia coli Lnt. This enzyme contai...

Psb27 is a membrane-extrinsic subunit of photosystem II (PSII) where it is involved in the assembly and maintenance of this large membrane protein complex that catalyzes one of the key reactions in the biosphere, the light-induced oxidation of water. Here, we report for the first time the structure of Psb27 that was not observed in the previous crystal structures of PSII due to its transient bi...

Numerous proteins act in concert to sculpt membrane compartments for cell signaling and metabolism. These proteins may act as curvature sensors, membrane benders, and scaffolding molecules. Here we show that endophilin, a critical protein for rapid endocytosis, quickly transforms from a curvature sensor into an active bender upon membrane association. We find that local membrane deformation doe...

Actinoporins are potent pore-forming toxins produced by sea anemones. They readily form pores in membranes that contain sphingomyelin. Molecular mechanism of pore formation involves recognition of membrane sphingomyelin, firm binding to the membrane accompanied by the transfer of the N-terminal region to the lipid-water interface and oligomerization of three to four monomers with accompanying p...

Gene-specific targeting of the Sin3 corepressor complex by DNA-bound repressors is an important mechanism of gene silencing in eukaryotes. The Sin3 corepressor specifically associates with a diverse group of transcriptional repressors, including members of the Mad family, that play crucial roles in development. The NMR structure of the complex formed by the PAH2 domain of mammalian Sin3A with t...

The effect of C-terminal amidation on the antimicrobial and hemolytic activities of antimicrobial peptides was studied using three cationic peptides which form amphiphilic α-helices when bound to membranes. The natural antimicrobial peptide PGLa, the designermade antibiotic MSI-103, and the cell-penetrating “model amphipathic peptide” (MAP) are all amidated in their original forms, and their bi...

We have used a novel assay based on protein fusions with lambda repressor to identify two small regions within phytochrome's carboxy-terminal domain that are capable of mediating dimerization. Using an in vivo assay, fusions between the DNA binding, amino-terminal domain of lambda repressor and fragments from oat PhyA phytochrome have been assayed for increased repressor activity, an indicator ...

Hydrophobic mismatch is a well-recognized principle in the interaction of transmembrane proteins with lipid bilayers. This concept was extended here to amphipathic membranolytic α-helices. Nine peptides with lengths between 14 and 28 amino acids were designed from repeated KIAGKIA motifs, and their helical nature was confirmed by circular dichroism spectroscopy. Biological assays for antimicrob...

Frizzled 4 belongs to the superfamily of G protein coupled receptors. The unstructured cytosolic tail of the receptor is essential for its activity. The mutation L501fsX533 in the fz4 gene results in a new COOH-tail of the receptor and causes a form of Familial exudative vitreoretinopathy. Here we show that the mutated tail is structured. Two amphipathic helices, displaying affinity for membran...