ProfilinFamilie

ProfilinFamilie refers to a group of small, highly conserved actin-binding proteins found in almost all eukaryotic cells. Members of this family regulate actin filament dynamics by binding to monomeric actin (G-actin) and to poly-L-proline-containing ligands, thereby influencing polymerization and organization of the cytoskeleton. In addition to binding G-actin, profilins interact with phosphatidylinositol-4,5-bisphosphate (PIP2) at membranes, linking actin dynamics to signaling pathways.

Structurally, profilins are compact proteins of roughly 129 amino acids that share a conserved fold with a hydrophobic actin-binding surface and a poly-L-proline binding site. Their activity is context-dependent: they sequester actin monomers to prevent spontaneous nucleation, yet promote filament growth when formins or other proline-rich proteins are present by delivering actin monomers to the growing end.

Profilin genes are widely distributed across eukaryotes. In humans, the best-characterized paralogs are PFN1 and PFN2, with broader tissue distribution and distinct regulatory properties; some species possess additional profilin paralogs with tissue- or development-specific expression. Profilins are not only essential for basic cell motility and morphology but also appear as plant or pollen allergens in humans, contributing to cross-reactive allergic responses.

Clinical and research relevance: PFN1 mutations have been linked to neurodegenerative conditions such as familial amyotrophic lateral sclerosis, while profilin studies continue to illuminate general mechanisms of actin dynamics and cytoskeletal regulation.

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