The membrane-attack complex (MAC) of the complement system forms transmembrane channels. These channels disrupt the phospholipid bilayer of target cells, leading to cell lysis and death. A number of proteins participate in the assembly of the MAC. Fr ...
The membrane-attack complex (MAC) of the complement system forms transmembrane channels. These channels disrupt the phospholipid bilayer of target cells, leading to cell lysis and death. A number of proteins participate in the assembly of the MAC. Freshly activated C5b binds to C6 to form a C5b-6 complex, then to C7 forming the C5b-7 complex. The C5b-7 complex binds to C8, which is composed of three chains (alpha, beta, and gamma), thus forming the C5b-8 complex. C5b-8 subsequently binds to C9 and acts as a catalyst in the polymerisation of C9. Active MAC has a subunit composition of C5b-C6-C7-C8-C9{n}. Perforin is a protein found in cytolytic T-cell and killer cells. In the presence of calcium, perforin polymerises into transmembrane tubules and is capable of lysing, non-specifically, a variety of target cells. There are a number of regions of similarity in the sequences of complement components C6, C7, C8-alpha, C8-beta, C9 and perforin. The X-ray crystal structure of a MACPF domain reveals that it shares a common fold with bacterial cholesterol dependent cytolysins (Pfam:PF01289) such as perfringolysin O. Three key pieces of evidence suggests that MACPF domains and CDCs are homologous: Functional similarity (pore formation), conservation of three glycine residues at a hinge in both families and conservation of a complex core fold [1].
This annexin-like domain can be found in astrotactin 2 (Astn-2), an integral membrane perforin-like protein linked to the planar cell polarity pathway in hair cells. The annexin-like domain is closest in fold to repeat three of human annexin V and si ...
This annexin-like domain can be found in astrotactin 2 (Astn-2), an integral membrane perforin-like protein linked to the planar cell polarity pathway in hair cells. The annexin-like domain is closest in fold to repeat three of human annexin V and similarly binds calcium, yet shares no sequence homology with it. Notably, this ASTN-2 annexin-like domain is closer in structure to human annexin repeat 3 than human annexin repeat 3 is to repeat 1. Annexin-like domains are known for their capacity to remodel membranes, triggered by calcium binding, and have also been suggested to be involved in the formation of pores in membranes both are possible biological roles of the ASTN-2 annexin-like domain [1].
Astrotactin-1 and 2 (ASTN1/2) are integral membrane proteins with a large C-terminal domain, extracellular for ASTN1 and endosome luminal for ASTN-2 [1,2]. They play critical roles in neurodevelopment, and ASTN-2 is also involved in the planar cell p ...
Astrotactin-1 and 2 (ASTN1/2) are integral membrane proteins with a large C-terminal domain, extracellular for ASTN1 and endosome luminal for ASTN-2 [1,2]. They play critical roles in neurodevelopment, and ASTN-2 is also involved in the planar cell polarity pathway in hair cells. This is a domain found in the middle of the C-terminal of ASTN-1 and 2, which comprises a fibronectin type III (Fn(III)) domain [1]. This domain located between the MACPF and annexin domains. The structure of Fn(III) from ASTN2 revealed an unexpected feature which has two additional beta strands folded across the core. The junction between EGF-4 and Fn(III) domains in ASTN2 (but not in ASTN1) is thought to be an inositol triphosphate binding site [1].
This is a beta-hairpin domain found at the C-terminal region of astrotactin 2 proteins (ASTN-2). ASTN-2 is an integral membrane perforin-like protein linked to the planar cell polarity pathway in hair cells. it consists of multiple polypeptide folds: ...
This is a beta-hairpin domain found at the C-terminal region of astrotactin 2 proteins (ASTN-2). ASTN-2 is an integral membrane perforin-like protein linked to the planar cell polarity pathway in hair cells. it consists of multiple polypeptide folds: a perforin-like domain, a minimal epidermal growth factor-like module, a fibronectin type III domain Fn (III) and an annexin-like domain as well as the beta hairpin domain which packs across the fibronectin domain [1].
