LetB 结构揭示了通过细菌外运输的道

Lipopolysaccharides (LPS) are crucial components of the outer membrane of Gram-negative bacteria, serving both structural and functional roles. It contributes to membrane stability and protects bacteria from host immune responses. LPS is composed of three major regions—lipid A, a core oligosaccharide, and an O antigen. The biosynthesis and assembly of LPS involve a highly coordinated set of enzymatic reactions and transport mechanisms. Additionally, LPS is recognized as an endotoxin,...

Biological membranes are more than just a barrier separating cell cytoplasm from the outside environment. They are highly dynamic and help maintain the integrity and physiological stability of the cells as well as membrane-bound organelles. Membranes also play vital roles in cell-to-cell and intracellular communication.
A large chunk of any biological membrane is composed of phospholipids. These lipids have a heterogeneous distribution across different subcellular organelles and even between...

Bacterial protein secretion involves translocation systems to ensure proteins reach their designated locations, including the plasma membrane, periplasm, outer membrane, or the external environment. These translocation systems are vital for bacterial physiology, supporting processes like membrane assembly, enzymatic activity in the periplasm, and interactions with the external environment. The division of labor between Sec and Tat pathways ensures efficiency in handling proteins with diverse...

The outermost layers of prokaryotic cells play a critical role in their survival, virulence, and interaction with the environment. These layers, often composed of polysaccharides, polypeptides, or proteins, form protective and adhesive structures that vary in organization and function.Capsules and Slime LayersCapsules are highly organized, tightly bound layers that firmly attach to the bacterial cell wall. Capsules are usually made of polysaccharides, though some are made of polypeptides. These...

Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a  motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel...

The translocon complex situated on the ER membrane is the main gateway for the protein secretory pathway. It facilitates the transport of nascent peptides into the ER lumen and their insertion into the ER membrane.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the...