Longin domain containing proteins as essential genes

SNAREs (Soluble NSF Attachment protein REceptors) are a superfamily of proteins whose members are responsible in eukaryotes for almost all events in the extracellular and intracellular secretory pathway. SNARE proteins are especially important for vesicular transport and (in animals) neurotransmitter release at synapses. These proteins are present in the membrane of the vesicle and the target cell and form a complex that promotes membrane fusion. In 2001, a family of vesicular v/R-SNAREs was identified that shared a conserved N-terminal domain. Due to their comparatively greater length with respect to 'Brevins', such as synaptobrevins, these proteins were thus named "Longins''. Consequently, their N-terminal domain was designated as the 'Longin domain'. A comparative analysis of major Eukaryotic taxa has demonstrated that Longins and their longin domains are conserved in all Eukaryotic taxa. In contrast, Brevins are a class of R-SNAREs present only in Opisthokonta (animals and fungi). Furthermore, evidence suggests that each eukaryotic genome contains a minimum of three Longin genes belonging to three subfamilies prototyped by Ykt6, Sec22b and VAMP7. Since all eukaryotes have Longins, these are likely to be essential genes. This thesis focuses on highlighting the crucial cellular roles of Longins in subcellular trafficking, which underlies their essential nature.