Two structural folds anchor proteins into the membrane; the alpha helix and beta barrel. Alpha helical proteins are found in all membranes, while beta barrel proteins are restricted the OM of bacteria, chloroplasts and mitochondria. How these proteins are assembled into the OM is poorly understood, although the bacterial BAM complex is essential for this. A detailed structuresof the substrate-bound BAM complex was presented. Here, I will discuss this structure and its mechanistic significance.
About 20-30% of the human proteome comprises integral membrane proteins. These are essential for proper cell functioning and are cotranslationally synthesized at the ER through the Sec61 translocon. Moreover, the ER contains other insertion factors that mediate membrane protein insertion such as EMC. The structure of human EMC was presented recently, providing mechanistic insight of membrane protein insertion. Here, I will discuss this structure as well as its current functional understanding.
Resistance to chemotherapeutics is a pressing problem in cancer therapy. This is often caused by ABC transporters that remove drugs from the cell. The export of toxic compounds by these proteins is powered by ATP hydrolysis. ABCG2 is a human transporter known to confer multidrug resistance in many tumors. Recently, detailed structures of ABCG2 in the apo state and bound to anticancer drugs were determined. Here, I will discuss these structures as well as their current functional understanding.
Bacteria display a large variety in cell shape but rely on peptidoglycan to maintain their shape. This is a mesh-like biopolymer that surrounds the cytoplasmic membrane and is made up of long glycan strands cross-linked by short peptides. The enzymes that catalyze peptidoglycan biosynthesis are known as peptidoglycan synthases. Recently, the structure of a novel a peptidoglycan synthase was elucidated. Here, I will discuss this structure as well as its functional understanding.
Glycoproteins are polypeptides decorated with oligosaccharides. They are prominent in eukaryotes and fulfill important biological roles e.g. cell signaling. Their biosynthesis occurs in the ER via the transfer of a carbohydrate precursor onto polypeptides. The precursor is obtained through a process catalyzed by glycosyltransferases. Recently, the detailed structure of yeast glucosyltransferase was reported. Here, I will discuss this structure as well as its current functional understanding.
Most proteins are exported linearly, while a subset is translocated folded. The bacterial Tat system is the best characterized system for the export of folded proteins. Although most mitochondria lack the Tat system, they retained a typical Tat-dependent substrate protein, RISP. In mitochondria, its export requires Bcs1 an AAA protein with the function of assembly factor. Recently, detailed structures of Bcs1 were reported. Here, I will discuss these as well as our functional understanding.
The threat of increasing antibiotic resistance emphasizes the need for novel drug targets. The inhibition of SPaseII, a key enzyme in the maturation of bacterial lipoproteins, by globomycin and myxovirescin shows that it is an effective drug target. The recent high-resolution structures of SPaseII complexed with these antibiotics revealed that they inhibit SPaseII by acting as a non-cleavable catalytic intermediate. Here, I will discuss these structures as well as their functional understanding.
Bacterial respiratory chains offer greater metabolic flexibility than mitochondrial ones, while they are energetically less efficient. E. coli, contains a respiratory system that allows it to grow aerobically and anaerobically. Aerobic grown E. coli cells express two terminal oxidases, cytochrome bo-oxidase and bd-oxidase, that reduce oxygen to water. Recently, a detailed structure of E. coli bd-oxidase was reported. Here, I will discuss this structure and its current functional understanding.
Mitochondria are essential eukaryotic organelles. Their activity depends on the correct functioning of its proteome. This comprises about 1500 proteins that are mainly nuclear-encoded and imported into the organelle. Therefore, mitochondria are equipped with specialized protein translocation nanomachines in their membranes. Recently, a detailed structure of the TOM complex was reported. Here, I will discuss this structure as well as its functional understanding.
Gram-negative bacteria possess dedicated protein secretion systems- type I through type VI. The type III injectisome is a nanomachine that spans the bacterial cell envelope and serves as protein-conducting channel. It is used by pathogens to transport virulence proteins directly into the host cytoplasm. Recent detailed structures have provided profound atomic insight into injectisome assembly and mechanism. Here I will discuss these structures as well as its current functional understanding.