Taxonomic distribution of proteins containing G2F domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing G2F domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Crystal structure and mutational analysis of a perlecan-binding fragmentof nidogen-1.

Hopf M, Gohring W, Ries A, Timpl R, Hohenester E
Nat Struct Biol. 2001; 8: 634-40

Nidogen, an invariant component of basement membranes, is amultifunctional protein that interacts with most other major basementmembrane proteins. Here, we report the crystal structure of the mousenidogen-1 G2 fragment, which contains binding sites for collagen IV andperlecan. The structure is composed of an EGF-like domain and an11-stranded beta-barrel with a central helix. The beta-barrel domain hasunexpected similarity to green fluorescent protein. A large surface patchon the beta-barrel is strikingly conserved in all metazoan nidogens.Site-directed mutagenesis demonstrates that the conserved residues areinvolved in perlecan binding.

Structural basis for the high-affinity interaction of nidogen-1 with immunoglobulin-like domain 3 of perlecan.

Kvansakul M, Hopf M, Ries A, Timpl R, Hohenester E
EMBO J. 2001; 20: 5342-5346

Nidogen and perlecan are large multifunctional basement membrane (BM) proteins conserved in all metazoa. Their high-affinity interaction, which is likely to contribute to BM assembly and function, is mediated by the central G2 domain in nidogen and the third immunoglobulin (IG)-like domain in perlecan, IG3. We have solved the crystal structure at 2.0 A resolution of the mouse nidogen-1 G2-perlecan IG3 complex. Perlecan IG3 belongs to the I-set of the IG superfamily and binds to the wall of the nidogen-1 G2 beta-barrel using beta-strands C, D and F. Nidogen-1 residues participating in the extensive interface are highly conserved, whereas the corresponding binding site on perlecan is more variable. We hypothesize that a second, as yet unidentified, activity of nidogen overlaps with perlecan binding and accounts for the unusually high degree of surface conservation in the G2 domain.

Recombinant nidogen consists of three globular domains and mediatesbinding of laminin to collagen type IV.

Fox JW, Mayer U, Nischt R, Aumailley M, Reinhardt D, Wiedemann H, Mann K, Timpl R, Krieg T, Engel J, et al.
EMBO J. 1991; 10: 3137-46

Recombinant mouse nidogen and two fragments were produced in mammaliancells and purified from culture medium without resorting to denaturingconditions. The truncated products were fragments Nd-I (positions 1-905)comprising the N-terminal globule and rod-like domain and Nd-IIcorresponding mainly to the C-terminal globule (position 906-1217).Recombinant nidogen was indistinguishable from authentic nidogen obtainedby guanidine dissociation from tumor tissue with respect to size,N-terminal sequence, CD spectra and immunochemical properties. Theydiffered in protease stability and shape indicating that the N-terminaldomain of the more native, recombinant protein consists of two globulesconnected by a flexible segment. This established a new model for theshape of nidogen consisting of three globes of variable mass (31-56 kDa)connected by either a rod-like or a thin segment. Recombinant nidogenformed stable complexes (Kd less than or equal to 1 nM) with laminin andcollagen IV in binding assays with soluble and immobilized ligands and asshown by electron microscopy. Inhibition assays demonstrated differentbinding sites on nidogen for both ligands with different specificities.This was confirmed in studies with fragment Nd-I binding to collagen IVand fragment Nd-II binding to laminin fragment P1. In addition,recombinant nidogen but not Nd-I was able to bridge between laminin or P1and collagen IV. Formation of such ternary complexes implicates a similarrole for nidogen in the supramolecular organization of basement membranes.

Amino acid sequence of mouse nidogen, a multidomain basement membrane protein with binding activity for laminin, collagen IV and cells.

Mann K, Deutzmann R, Aumailley M, Timpl R, Raimondi L, Yamada Y, Pan TC, Conway D, Chu ML
EMBO J. 1989; 8: 65-72

The whole amino acid sequence of nidogen was deduced from cDNA clones isolated from expression libraries and confirmed to approximately 50% by Edman degradation of peptides. The protein consists of some 1217 amino acid residues and a 28-residue signal peptide. The data support a previously proposed dumb-bell model of nidogen by demonstrating a large N-terminal globular domain (641 residues), five EGF-like repeats constituting the rod-like domain (248 residues) and a smaller C-terminal globule (328 residues). Two more EGF-like repeats interrupt the N-terminal and terminate the C-terminal sequences. Weak sequence homologies (25%) were detected between some regions of nidogen, the LDL receptor, thyroglobulin and the EGF precursor. Nidogen contains two consensus sequences for tyrosine sulfation and for asparagine beta-hydroxylation, two N-linked carbohydrate acceptor sites and, within one of the EGF-like repeats an Arg-Gly-Asp sequence. The latter was shown to be functional in cell attachment to nidogen. Binding sites for laminin and collagen IV are present on the C-terminal globule but not yet precisely localized.