Lipid bilayer strengthens the cooperative network of membrane proteins.

Although membrane proteins fold and function in a lipid bilayer constituting cell membranes, their structure and functionality can be recapitulated in diverse amphiphilic assemblies whose compositions deviate from native membranes. It remains unclear how various hydrophobic environments can stabilize membrane proteins and whether lipids play any role therein. Here, using the evolutionary unrelated α-helical and β-barrel membrane proteins of , we find that the hydrophobic thickness and the strength of amphiphile- amphiphile packing are critical environmental determinants of membrane protein stability.

Lipid bilayer induces contraction of the denatured state ensemble of a helical-bundle membrane protein.

Defining the denatured state ensemble (DSE) and disordered proteins is essential to understanding folding, chaperone action, degradation, and translocation. As compared with water-soluble proteins, the DSE of membrane proteins is much less characterized. Here, we measure the DSE of the helical membrane protein GlpG of () in native-like lipid bilayers.

Pre-termination Transcription Complex: Structure and Function.

Rho is a general transcription termination factor playing essential roles in RNA polymerase (RNAP) recycling, gene regulation, and genomic stability in most bacteria. Traditional models of transcription termination postulate that hexameric Rho loads onto RNA prior to contacting RNAP and then translocates along the transcript in pursuit of the moving RNAP to pull RNA from it. Here, we report the cryoelectron microscopy (cryo-EM) structures of two termination process intermediates.

Cryo-EM structure of the insect olfactory receptor Orco.

The olfactory system must recognize and discriminate amongst an enormous variety of chemicals in the environment. To contend with such diversity, insects have evolved a family of odorant-gated ion channels comprised of a highly conserved co-receptor (Orco) and a divergent odorant receptor (OR) that confers chemical specificity. Here, we present the single-particle cryo-electron microscopy structure of an Orco homomer from the parasitic fig wasp Apocrypta bakeri at 3.

Structure of the Cdc48 ATPase with its ubiquitin-binding cofactor Ufd1-Npl4.

Many polyubiquitinated proteins are extracted from membranes or complexes by the conserved ATPase Cdc48 (in yeast; p97 or VCP in mammals) before proteasomal degradation. Each Cdc48 hexamer contains two stacked ATPase rings (D1 and D2) and six N-terminal (N) domains. Cdc48 binds various cofactors, including the Ufd1-Npl4 heterodimer.

Visualization of ligand-induced transmembrane signaling in the full-length human insulin receptor.

Insulin receptor (IR) signaling plays a critical role in the regulation of metabolism and growth in multicellular organisms. IRs are unique among receptor tyrosine kinases in that they exist exclusively as covalent (αβ) homodimers at the cell surface. Transmembrane signaling by the IR can therefore not be based on ligand-induced dimerization as such but must involve structural changes within the existing receptor dimer.

UtpA and UtpB chaperone nascent pre-ribosomal RNA and U3 snoRNA to initiate eukaryotic ribosome assembly.

Early eukaryotic ribosome biogenesis involves large multi-protein complexes, which co-transcriptionally associate with pre-ribosomal RNA to form the small subunit processome. The precise mechanisms by which two of the largest multi-protein complexes-UtpA and UtpB-interact with nascent pre-ribosomal RNA are poorly understood. Here, we combined biochemical and structural biology approaches with ensembles of RNA-protein cross-linking data to elucidate the essential functions of both complexes.

Expression and Purification of the Individual Bam Components BamB-E.

BamB, BamC, BamD, and BamE are lipoproteins that, along with the integral membrane protein BamA, form the β-barrel assembly machinery (BAM) complex in the outer-membrane of Gram-negative bacteria. Elucidating the roles that these lipoproteins play in the β-barrel assembly process requires both structural and functional studies that rely on milligram quantities of pure protein. Here, we describe a simple protocol for expressing individual BamB-BamE proteins in Escherichia coli and purifying them by nickel affinity and size-exclusion chromatography.

Sequence and expression of an α-amylase gene in four related species of prickleback fishes (Teleostei: Stichaeidae): ontogenetic, dietary, and species-level effects.

Partial α-amylase gene sequences were determined and α-amylase gene expression was quantified in four species of carnivorous, omnivorous, and herbivorous prickleback fishes (family Stichaeidae) to assess the effects of ontogeny, diet, and species on expression of this gene. Pairwise comparison of α-amylase nucleotide sequences revealed 96-98 % identity, and comparison of amino acid portions revealed 93-95 % similarity among the four prickleback species. Expression was determined using in situ hybridization and intensity of expression quantified using image analysis.

The bacterial outer membrane β-barrel assembly machinery.

β-Barrel proteins found in the outer membrane of Gram-negative bacteria serve a variety of cellular functions. Proper folding and assembly of these proteins are essential for the viability of bacteria and can also play an important role in virulence. The β-barrel assembly machinery (BAM) complex, which is responsible for the proper assembly of β-barrels into the outer membrane of Gram-negative bacteria, has been the focus of many recent studies.

Crystallographic analysis of the C-terminal domain of the Escherichia coli lipoprotein BamC.

In Gram-negative bacteria, the BAM complex catalyzes the essential process of assembling outer membrane proteins. The BAM complex in Escherichia coli consists of five proteins: one β-barrel membrane protein, BamA, and four lipoproteins, BamB, BamC, BamD and BamE. Here, the crystal structure of the C-terminal domain of E.

Crystal structure of β-barrel assembly machinery BamCD protein complex.

The β-barrel assembly machinery (BAM) complex of Escherichia coli is a multiprotein machine that catalyzes the essential process of assembling outer membrane proteins. The BAM complex consists of five proteins: one membrane protein, BamA, and four lipoproteins, BamB, BamC, BamD, and BamE. Here, we report the first crystal structure of a Bam lipoprotein complex: the essential lipoprotein BamD in complex with the N-terminal half of BamC (BamC(UN) (Asp(28)-Ala(217)), a 73-residue-long unstructured region followed by the N-terminal domain).

Structural characterization of Escherichia coli BamE, a lipoprotein component of the β-barrel assembly machinery complex.

In Escherichia coli, the BAM complex catalyzes the essential process of assembling outer membrane proteins (OMPs). This complex consists of five proteins: one membrane-bound protein, BamA, and four lipoproteins, BamB, BamC, BamD, and BamE. Despite their importance in OMP biogenesis, there is currently a lack of functional and structural information on the BAM complex lipoproteins.

Crystal structure of Escherichia coli BamB, a lipoprotein component of the β-barrel assembly machinery complex.

In Gram-negative bacteria, the BAM (β-barrel assembly machinery) complex catalyzes the essential process of assembling outer membrane proteins. The BAM complex in Escherichia coli consists of five proteins: one β-barrel membrane protein, BamA, and four lipoproteins, BamB, BamC, BamD, and BamE. Despite their role in outer membrane protein biogenesis, there is currently a lack of functional and structural information on the lipoprotein components of the BAM complex.