Complement component C4 is a non-enzymatic component of C3 and C5 convertases and essential for the propagation of the classical complement pathway. It covalently binds to immunoglobulins and immune complexes and enhances the solubilization of immune ...
Complement component C4 is a non-enzymatic component of C3 and C5 convertases and essential for the propagation of the classical complement pathway. It covalently binds to immunoglobulins and immune complexes and enhances the solubilization of immune aggregates and clearance through CR1 on erythrocytes. C4 is cleaved into the fragments C4a and C4b by MASP-2 protease. C4A isotype is responsible for effective binding to form amide bonds with immune aggregates or antigens, whereas C4B isotype catalyses the transacylation of the thioester carbonyl group to form ester bonds with carbohydrate antigens. This entry represents the macroglobulin 1 (MG1) domain found at the N-terminal of C4 [1].
This is the MG2 (macroglobulin) domain of alpha-2-macroglobulin in eukaryotes [1]. Alpha-2-macroglobulins (A2Ms) are plasma proteins that trap and inhibit a broad range of proteases and are major components of the eukaryotic innate immune system. How ...
This is the MG2 (macroglobulin) domain of alpha-2-macroglobulin in eukaryotes [1]. Alpha-2-macroglobulins (A2Ms) are plasma proteins that trap and inhibit a broad range of proteases and are major components of the eukaryotic innate immune system. However, A2M-like proteins were identified in pathogenically invasive bacteria and species that colonize higher eukaryotes. This domain is found in eukaryotic and bacterial proteins. In human A2Ms, this domain is termed macroglobulin-like (MG) domain 2 and in Salmonella enterica ser A2Ms, this is domain 4 [2] [3].
Alpha-2-macroglobulins (A2Ms) are plasma proteins that trap and inhibit a broad range of proteases and are major components of the eukaryotic innate immune system. However, A2M-like proteins were identified in pathogenically invasive bacteria and spe ...
Alpha-2-macroglobulins (A2Ms) are plasma proteins that trap and inhibit a broad range of proteases and are major components of the eukaryotic innate immune system. However, A2M-like proteins were identified in pathogenically invasive bacteria and species that colonize higher eukaryotes. This domain is found in eukaryotic and bacterial proteins. In human A2Ms, this domain encompasses macroglobulin-like domain MG5 and 6 including bait region. In Salmonella enterica ser A2Ms, this domain encompasses MG7 and MG8 including the bait region [1] [2]. The Bait region is cleaved by proteases, followed by a large conformational change that blocks the target protease within a cage-like complex. This model of protease entrapment is recognised as the Venus flytrap mechanism [1].
C3a, C4a and C5a anaphylatoxins are protein fragments generated enzymatically in serum during activation of complement molecules C3, C4, and C5. They induce smooth muscle contraction. These fragments are homologous to a three-fold repeat in fibulins. ...
C3a, C4a and C5a anaphylatoxins are protein fragments generated enzymatically in serum during activation of complement molecules C3, C4, and C5. They induce smooth muscle contraction. These fragments are homologous to a three-fold repeat in fibulins.
Complement C4 is organised in 12 structural domains, with eight macroglobulin (MG) domains forming the core of the molecule. They have a thioester domain (TED, Pfam:PF07678), a large helical domain inserted in the CUB (complement C1r/C1s, Uegf, Bmp1) ...
Complement C4 is organised in 12 structural domains, with eight macroglobulin (MG) domains forming the core of the molecule. They have a thioester domain (TED, Pfam:PF07678), a large helical domain inserted in the CUB (complement C1r/C1s, Uegf, Bmp1) domain [5] which consists of two antiparallel beta-sheets. This entry covers a fraction of the CUB domain corresponding to the C-terminal part (residues 1323-1389 in human C4A/B) as this domain is made up of residues located apart in these sequences [5].
Sequence similarity between netrin UNC-6 and C345C complement protein family members, and hence the existence of the UNC-6 module, was first reported in [1]. Subsequently, many additional members of the family were identified on the basis of sequence ...
Sequence similarity between netrin UNC-6 and C345C complement protein family members, and hence the existence of the UNC-6 module, was first reported in [1]. Subsequently, many additional members of the family were identified on the basis of sequence similarity between the C-terminal domains of netrins, complement proteins C3, C4, C5, secreted frizzled-related proteins, and type I pro-collagen C-proteinase enhancer proteins (PCOLCEs), which are homologous with the N-terminal domains of tissue inhibitors of metalloproteinases (TIMPs). The TIMPs are classified as a separate family in Pfam (Pfam:PF00965) [2]. This expanded domain family has been named as the NTR module [2].
