Neglected but amazingly diverse type IVb pili

Fimbriae and pili are specialized bacterial surface structures that play pivotal roles in adhesion, genetic exchange, and motility. Composed primarily of pilin protein, these hairlike appendages are crucial for bacterial survival and pathogenicity in various environments.Fimbriae: Adhesion and PathogenicityFimbriae are fine, filamentous structures measuring 2–10 nanometers in diameter and are densely distributed on the bacterial cell surface. They facilitate bacterial adhesion to abiotic...

The intermediate filaments are an essential component of the cytoskeleton. Presently six types of intermediate filament have been identified. Type I and II are acidic and basic keratin proteins. Type III is of mesodermal origin and comprises four proteins: vimentin, desmin, glial fibrillary acidic protein (GFAP), and peripherin. Vimentin is commonly found in mesenchymal cells, desmin in muscle cells, GFAP in astrocytes, while peripherin is found in peripheral nervous system neurons (PNS). Type...

Type IV collagen is a 400 nm long, network-forming collagen that acts as a barrier between the epithelial and endothelial cells. Type IV collagen  forms the backbone of the basement membrane by scaffolding with laminin, entactin, proteoglycans, and fibronectin. Apart from rendering structural support to the basement membrane, it also helps entail signaling potentials necessary for both pathological and physiological functions.
A type IV collagen molecule has six alpha chains which can exist in...

Archaeal surface appendages are highly specialized structures essential for environmental adaptation, encompassing roles in adhesion, biofilm formation, and motility. Among these appendages, pili and archaella stand out for their distinct morphologies and functionalities, enabling archaea to thrive in diverse and often extreme environments.Pili: Adhesion and Biofilm FormationPili are filamentous structures assembled from pilin protein subunits, primarily contributing to adhesion and biofilm...

Bacterial cells were initially considered simple, randomly organized structures lacking a cytoskeleton. However, the discovery of cytoskeleton homologs in bacteria led to the change of this opinion. Bacterial cytoskeletal filaments regulate the cell shape, cell polarity, cell division, and partitioning of plasmids during cell division. It was later discovered that bacterial cytoskeletal proteins, mainly actin and tubulin homologs, are diverse compared to their eukaryotic counterparts. On the...

Fibril-associated collagens are a type of collagens present in the extracellular matrix with interrupted triple helices or FACIT (Fibril-associated collagens interrupted triple-helices). FACIT help connect and attach the collagen fibrils with each other as well as with other proteins of the extracellular matrix.
For example, the type II collagen fibrils in cartilage have covalently bound type IX fibril-associated collagens at regular intervals. Other types of fibril-associated collagens are...