Biogenesis of lysosome-related organelles complex 1 subunit 5 (IPR017243)

Short name: Bloc1s5

Overlapping homologous superfamilies


Family relationships



Lysosomes are membrane-bound organelles found in animals that are involved in degradation of endogenous and exogenous macromolecules [PMID: 15261680]. Lysosome-related organelles occur in specific cell types and fulfil specialised functions e.g. melanosomes which synthesise and store pigments in higher eukaryotes. Lysosome biogenesis is linked to the to the secretory and endocytic pathways for protein and lipid trafficking.

One of the protein complexes involved in this process is biogenesis of lysosome-related organelles complex 1 (BLOC-1). This complex consists of seven distinct subunits: dysbindin, pallidin, muted, snapin, cappuccino, and BLOS1-3 subunits [PMID: 21998198]. Apart from BLOCS3 all of these subunits are predicted to form coiled-coil structures. BLOC-1 can be found in the cytosol and also associated with membranes. Protein interaction studies suggest that this complex interacts with a number of proteins including syntaxin, filametous actin, dystrobrevin and mysopryn, though the molecluar function of this complex is not yet known. Mutations in BLOC-1 subunits are associated with Hermansky-Pudlak syndrome - a disorder characterised by deficiencies in melanosomes, platelet-dense granules and other lysosome-related organelles. Cells that lack lysosome-related organelles express BLOC-1 but do not appear to need it for lysosome biosynthesis. In concert with the AP-3 complex, the BLOC-1 complex is required to target membrane protein cargos into vesicles assembled at cell bodies for delivery into neurites and nerve terminals [PMID: 21998198].

This group represents the subunit 5 (also known as the muted subunit) of BLOC-1 [PMID: 11912185]. In mice, defects in this protein are the cause of the Muted (mu) mutant, which is characterised by light eyes at birth, hypopigmentation of the coat, platelet storage pool deficiency and lysosomal hyposecretion [PMID: 11912185].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

No terms assigned in this category.

Cellular Component

GO:0031083 BLOC-1 complex
GO:0030133 transport vesicle

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.