Clock-interacting pacemaker or clock-interacting circadian protein (CIPC) is an additional negative-feedback regulator of the circadian clock, through inhibition of CLOCK-BMAL1 activity [, , ]. Studies in knockout mice suggest that it may not be critically required for basic clock function [].
Carbohydrate-binding modules (CBM) have been classified into more than 40families according to sequence homology. Several cellulolytic enzymesshare a conserved region of about 150 amino acid residues, the CBM3 domain[]. It has been classified in three different subtypes, termed family IIIa, IIIb and IIIc. The family IIIa (scaffoldin) and IIIb (mainly free enzymes) are closely similar in their primary structures and both types bind strongly to crystalline cellulose [, ]. Members of the family IIIc, fail to bind crystalline cellulose, but serve in a 'helper' capacity by feeding a single incoming cellulose chain into the active site of the neighbouring catalytic module pending hydrolysis [, ].The CBM3 domain is mainly found C-terminal to the catalytic domain, whichcorrespond to a wide range of bacterial glycosyl hydrolases like family 9, family 5 and family 10.The crystal structure of CBM3 has been solved []. Itconsists of nine β-strands which form a compact domain that has an overallprismatic shape. It is arranged in two antiparallel β-sheets that stackface-to-face to form a beta sandwich with jelly roll topology. Two definedsurfaces, located on opposite sides of the molecule, contain conserved polarand aromatic residues which are probably involved in the binding of the CBM tocellulose [, ]. The first one forms a planar strip whereas the second one forms a shallow groove.Some proteins known to contain a CBM3 domain are listed below:Clostridial cellulosomal scaffolding proteins cipA, cipC and cbpA. Theypromote the binding of cellulose to the catalytic domains of thecellulolytic enzymes.Bacterial cellulases A, B, F, G, I, N, Y, Z (Endo-1,4-beta-glucanase, ).This entry represents the CBM3 domain, which is also known as cellulose-binding domain family III (CBD III).
Carbohydrate-binding modules (CBM) have been classified into more than 40families according to sequence homology. Several cellulolytic enzymesshare a conserved region of about 150 amino acid residues, the CBM3 domain[]. It has been classified in three different subtypes, termed family IIIa, IIIb and IIIc. The family IIIa (scaffoldin) and IIIb (mainly free enzymes) are closely similar in their primary structures and both types bind strongly to crystalline cellulose [, ]. Members of the family IIIc, fail to bind crystalline cellulose, but serve in a 'helper' capacity by feeding a single incoming cellulose chain into the active site of the neighbouring catalytic module pending hydrolysis [, ].The CBM3 domain is mainly found C-terminal to the catalytic domain, whichcorrespond to a wide range of bacterial glycosyl hydrolases like family 9, family 5 and family 10.The crystal structure of CBM3 has been solved []. Itconsists of nine β-strands which form a compact domain that has an overallprismatic shape. It is arranged in two antiparallel β-sheets that stackface-to-face to form a beta sandwich with jelly roll topology. Two definedsurfaces, located on opposite sides of the molecule, contain conserved polarand aromatic residues which are probably involved in the binding of the CBM tocellulose [, ]. The first one forms a planar strip whereas the second one forms a shallow groove.Some proteins known to contain a CBM3 domain are listed below:Clostridial cellulosomal scaffolding proteins cipA, cipC and cbpA. Theypromote the binding of cellulose to the catalytic domains of thecellulolytic enzymes.Bacterial cellulases A, B, F, G, I, N, Y, Z (Endo-1,4-beta-glucanase, ).This entry represents the CBM3 domain, which is also known as cellulose-binding domain family III (CBD III).
The immunoglobulin (Ig) like fold, which consists of a β-sandwich of seven or more strands in two sheets with a greek-key topology, is one of the most common protein modules found in animals. Many different unrelated proteins share an Ig-like fold, which is often involved in interactions, commonly with other Ig-like domains via their β-sheets []. Of these, the "early"set (E set) domains are possibly related to the immunoglobulin () and/or fibronectin type III () Ig-like protein superfamilies. Ig-like E set domains include:C-terminal domain of certain transcription factors, such as the pro-inflammatory transcription factor NF-kappaB, and the T-cell transcription factors NFAT1 and NFAT5 [].Ig-like domains of sugar-utilising enzymes, such as galactose oxidase (C-terminal domain), sialidase (linker domain), and maltogenic amylase (N-terminal domain).C-terminal domain of arthropod haemocyanin, where many loops are inserted into the fold. These proteins act as dioxygen-transporting proteins.C-terminal domain of class II viral fusion proteins. These envelope glycoproteins are responsible for membrane fusion with target cells during viral invasion.Cytomegaloviral US (unique short) proteins. These type I membrane proteins help suppress the host immune response by modulating surface expression of MHC class I molecules [].Molybdenium-containing oxidoreductase-like dimerisation domain found in enzymes such as sulphite reductase.ML domains found in cholesterol-binding epididymal secretory protein E1, and in a major house-dust mite allergen; ML domains are implicated in lipid recognition, particularly the recognition of pathogen-related products.Rho-GDI-like signalling proteins, which regulate the activity of small G proteins [].Cytoplasmic domain of inward rectifier potassium channels such as Girk1 and Kirbac1.1. These channels act as regulators of excitability in eukaryotic cells.N-terminal domain of transglutaminases, including coagulation factor XIII; many loops are inserted into the fold in these proteins. These proteins act to catalyse the cross-linking of various protein substrates [].Filamin repeat rod domain found in proteins such as the F-actin cross-linking gelation factor ABP-120. These proteins interact with a variety of cellular proteins, acting as signalling scaffolds [].Arrestin family of proteins, which contain a tandem repeat of two elaborated Ig-like domains contacting each other head-to-head. These proteins are key to the redirection of GPCR signals to alternative pathways [].C-terminal domain of arginine-specific cysteine proteases, such as Gingipain-R, which act as major virulence factors of Porphyromonas gingivalis (Bacteroides gingivalis).Copper-resistance proteins, such as CopC, which act as copper-trafficking proteins [].Cellulosomal scaffoldin proteins, such as CipC module x2.1. These proteins act as scaffolding proteins of cellulosomes, which contain cellulose-degrading enzymes [].Quinohaemoprotein amine dehydrogenases (A chain), which contain a tandem repeat of two Ig-like domains. These proteins function in electron transfer reactions.Internalin Ig-like domains, which are truncated and fused to a leucine-rich repeat domain. These proteins are required for host cell invasion of Listeria species.
