This entry represents complement component C7, a subunit of the membrane attack complex (MAC) which forms pores in the membranes of cells of invading organisms. C7 anchors the MAC to the membrane. MAC forms when C5 is cleaved into C5a and C5b, and C5b binds sequentially C6, C7, C8 and multiple copies of the pore-forming subunit C9 []. The structure of C7 has been solved and C7 contains a several domains, which from N to C terminus are: TSP type-1, LDL-receptor class A, MACPF, EGF-like, another TSP type-1 and two sushi domains []. Variants of C7 are associated with immunodeficiency diseases and susceptibility to infection such as meningococcal disease caused by Neisseria meningitidis [].
This entry represents a peptidase C7 domain, which is found in HAV papain-like proteases p48 and p29 [, ].Hypoviruses are positive-strand RNA mycoviruses that attenuate virulence of their pathogenic fungal hosts [E1]. They employ a gene expression strategy that involves the autocatalytic processing of the N-terminal portion of encoded polyproteins by papain-like protease domains. The prototypic hypovirus CHV-1/EP713, responsible for virulence attenuation (hypovirulence) of the chestnut blight fungus Cryphonectria parasitica, encodes two contiguous open reading frames (ORFs) designated ORF A and ORF B, which contain N-terminal proteases p29 and p48, respectively. Protease p29 functions as a suppressor of the RNA silencing defense response, while p48 is required for viral RNA replication [, , ]. The HAV papain-like protease p29 is a cysteine protease, which forms the peptidase family C7 [E2]. A Cys and a His catalytic residue are essential for autocatalytic cleavage at a glycine dipeptide clevage site located at the C- terminus of the domain [, , ]. The HAV papain-like protease p48 is a cysteine protease, which forms the peptidase family C8 [E3]. A Cys anda His catalytic residue are essential for autocatalytic cleavage between the cleavage site residues Gly and Ala located at the C terminus of the domain [, , ].
This family includes cytochromes c7 and c7-type. In cytochromes c7 all three haems are bis-His coordinated, while in c7-type the last haem is His-Met coordinated []. Desulfuromonas acetoxidans and Geobacter metallireducens cytochrome c7 participate in the anaerobic iron respiration, but Geobacter metallireducens cytochrome c7 hasn't a Fe(III) reductase activity [].This entry also includes cytochrome c nitrite reductase subunit NrfH from Desulfovibrio vulgaris which forms a complex with cytochrome c nitrite reductase NrfA [].
This Kazal domain is found in the factor I-like modules (FIMs) region on the C terminus of complement component C7 proteins. Complement component C7 is a subunit of the membrane attack complex (MAC), a fundamental machinery in the mammalian innate immunity. KAZAL domains are common in serine protease inhibitors [].
This superfamily represents the N-terminal of muramoyl-tetrapeptide carboxypeptidase, also known as LD-carboxypeptidase A. The enzyme hydrolyses a peptide bond between a di-basic amino acid and the C-terminal D-alanine in the tetrapeptide moiety in peptidoglycan. This cleaves the bond between an L- and a D-amino acid. This activity is has a role ine in murein recycling [, ]. Proteins containing this domain also include the microcin c7 self-immunity protein .
This superfamily represents the C-terminal domain of the LD-carboxypeptidase A. Muramoyl-tetrapeptide carboxypeptidase or LD-carboxypeptidase A hydrolyses a peptide bond between a di-basic amino acid and the C-terminal D-alanine in the tetrapeptide moiety in peptidoglycan. This cleaves the bond between an L- and a D-amino acid. The function of this activity is in murein recycling [, ]. Proteins containing this domain alsoinclude the microcin c7 self-immunity protein []and microcin immunity protein MccF [].
This entry includes proteins belonging to the MEROPS peptidase family S66, such as muramoyl-tetrapeptide carboxypeptidase and the microcin c7 self-immunity protein . Muramoyl-tetrapeptide carboxypeptidase, also known as LD-carboxypeptidase A, hydrolyses a peptide bond between a di-basic amino acid and the C-terminal D-alanine in the tetrapeptide moiety in peptidoglycan. This cleaves the bond between an L- and a D-amino acid. This activity has a role in murein recycling [, ].
This entry represents the C-terminal domain of the LD-carboxypeptidase A. Muramoyl-tetrapeptide carboxypeptidase or LD-carboxypeptidase A hydrolyses a peptide bond between a di-basic amino acid and the C-terminal D-alanine in the tetrapeptide moiety in peptidoglycan. This cleaves the bond between an L- and a D-amino acid. The function of this activity is in murein recycling [, ]. Proteins containing this domain also include the microcin c7 self-immunity protein []and microcin immunity protein MccF [].
This entry represents a domain found in the Trm5/Tyw2-type methyltransferase. Trm5 and Tyw2 are S-adenosylmethionine-dependent methyltransferases involved in tRNA methylation []. Wybutosine synthesis is a multienzymatic process that comprises six sequential enzymatic reactions involving five enzymes. The initial step, the formation of m1G-37 (guanosine-37 methylated in the N1 position) in precursor tRNAPhe is catalysed by tRNA wybutosine-synthesising protein 5 (Trm5). Tyw2 catalyses the second step, consisting of the alpha-amino-alpha-carboxypropyl (acp) group being transferred from S-AdoMet to the side chain at the C7 position of 4-demethylwyosine (imG-14) to produce wybutosine-86 [].
This entry includes proteins belonging to the MEROPS peptidase family S66, such as muramoyl-tetrapeptide carboxypeptidase and the microcin c7 self-immunity protein . Muramoyl-tetrapeptide carboxypeptidase, also known as LD-carboxypeptidase A, hydrolyses a peptide bond between a di-basic amino acid and the C-terminal D-alanine in the tetrapeptide moiety in peptidoglycan. This cleaves the bond between an L- and a D-amino acid. This activity has a role in murein recycling [, ]. The structure of Pseudomonas aeruginosa LD-carboxypeptidase showed that the enzyme consists of an N-terminal β-sheet and a C-terminal β-barrel domain []. This entry represents the N-terminal domain.
This domain is found in complement component proteins, complement component factor 1 and agrin. Complement components C5b, C6, C7 C8 and C9 are the constituents of the membrane attack complex (MAC) that plays a key role in the innate and adaptive immune response by forming pores in the plasma membrane of target cells. Its assembly is initiated by protelytic cleavage of C5 into C5a and C5b. C5b binds sequentially C6, C7, C8 and multiple copies of the pore-forming subunit C9. Factor I is responsible for cleaving alpha chains of C4B and C3B in the presence of the cofactors C4-binding protein and factor H respectively. Agrin is a component of the basal lamina that causes the aggregation of acetylcholine receptors and acetylcholine-esterase on the surface of muscle fibres of the neuromuscular junction.
Cytochromes c (cytC) can be defined as electron-transfer proteins having one or several haem c groups, bound to the protein by one or, more generally, two thioether bonds involving sulphydryl groups of cysteine residues. The fifth haem iron ligand is always provided by a histidine residue. CytC possess a wide range of properties and function in a large number of different redox processes []. Ambler []recognised four classes of cytC.Class III comprises the low redox potential multiple haem cytochromes: cyt C7 (trihaem), C3 (tetrahaem),and high-molecular-weight cytC, HMC (hexadecahaem), with only 30-40 residues per haem group. The haem c groups, all bis-histidinyl coordinated,are structurally and functionally nonequivalent and present different redoxpotentials in the range 0 to -400 mV []. The 3D structures of a number of cyt C3 proteins have been determined. The proteinsconsist of 4-5 α-helices and 2 β-strands wrapped around a compactcore of four non-parallel haems, which present a relatively high degree of exposure to the solvent. The overall protein architecture, haem plane orientations and iron-iron distances are highly conserved [].
In proteins belonging to the c-type cytochrome family [], the haem group is covalently attached by thioether bonds to two conserved cysteine residues located in the cytochrome c centre. Cytochromes c typically function in electron transfer, but c-type cytochrome centres are also found in the active sites of many enzymes.This domain contains multiple CxxCH motifs. There are a variable number of helices, as well as a little beta structure present in multihaem cytochromes, but they do not form a true structural fold. Cytochrome (cyt) c3-like proteins are multihaem cytochromes, including cyt c3 with four haem groups [], cyt c7 (cyt c551.5) with three haem groups (deletion of one cyt c3 haem-binding site), nine-haem cyt c (tandem repeat of two cyt c3-like domains with an additional haem-binding site), and 16-haem cyt c HmcA (tandem repeat of four cyt c3-like domains). The photosynthetic reaction centre composed of a cytochrome subunit is also a multihaem cytochrome []. In addition, the di-haem elbow motif shows a similar structure, the main characteristic feature of this motif being the packing of its two haems; many members of this group of proteins contain one or more complete motifs flanked by incomplete motifs and/or other domains. For example, the di-haem elbow motif is present in the multihaem cytochrome domain found in the periplasmic nitrate reductase subunit NapB [], in hydroxylamine oxioreductase HAO (contains 3 complete motifs), in cyt c554 (contains one complete motif), in cyt c nitrite reductase, and in the N-terminal domain of flavocytochrome c3 (respiratory fumarate reductase).
