Two-domain proteins

Boumann, U., et al. Three-dimensional structure of the alkaline protease of Pseudomonas aeruginosa, a two-domain protein with a calcium binding parallel beta roll motif. EMBO J. 12 3357-3364, 1993. 

Fesik and co-workers have reported a study on the conserved two-domain protein SP14.3 from S. pneumoniae.116 Although the function of this protein was not known, it was believed to be essential for S. pneumoniae and thus represented a target for development of therapeutics. Intriguingly, although the NMR structure indicated that the C- and N-terminal domains are separated by only a three-residue linker, a single order tensor could not be determined... 

Both famesyltransferases70 761 and geranylgeranyl-transferases72/77 78b have been characterized, and the three- dimensional structure of the former has been established.73 75-76 The two-domain protein contains a seven-helix crescent-shaped hairpin domain and an a,a-barrel similar to that in Fig. 2-29. A bound zinc ion in the active site may bind the -S group of the substrate protein after the famesyl diphosphate has been bound into the active site.76 79 These enzymes are thought to function by a carbocation mechanism as shown in Eq. 22-3 and with the indicated inversion of configuration.71... 

The Vo is made of subunits acc c"de. Subunits c, c, and c" are proteolipid isoforms each containing one essential lipid-exposed glutamate residue. The proteolipids in the V-ATPase are twice the size compared with the F-ATPase proteolipids, and it is assumed that the four transmembrane a helix c- and c -subunits are a result of an early gene fusion event. Subunit c" has two lipid-exposed glutamates, but only one of them is essential for proton pumping. The 100-kDa subunit a is a two-domain protein with a... 

It has been shown that the hierarchical approach illustrated above for the case of a two-domain protein can be performed at a more fundamental level in order to account for the cooperative folding behavior of single-domain proteins (Freire and Murphy, 1991). This approach involves the use of the crystallographic structure of a pro-... 

Figure 7-26. Differential scanning calorimetry of the melting of a hypothetical two-domain protein.

The copper-containing nitrite reductase from A. cycloclastes may also have evolved from this ancestral oxidase. Nitrite reductase is a two-domain protein that functions as a trimeric molecule. During its evolution from the ancestral copper oxidase, a gene inversion must have occurred, so that domain 2 of the ancestral oxidase is now domain 1 of nitrite reductase. Domain 1 of the ancestral oxidase lost its type-1 copper but has become domain 2 in nitrite reductase after the gene inversion. 

Fig. 13. The alp hydrolase fold and it variations. (A) cudnase, (B) dienelactone hydrolase and haloalkane dehalogenase, (C) wheat carboxypepddase, (D) RmL, (E) hPL, (F) GcL and AChE the three catalytic residues, always in the order Ser, Asp/Glu, and His, appear as dark dots. The folds are aligned in such a way as to show the structural homologies within the hydrolytic domains, somewhat divorced from the N-terminal part of the sheet. The hPL is a two-domain protein, and the location of the additional C-terminal domain is indicated.

Lykke-Andersen, J.. Garrett, R.A. and Kjems. J. (1996). Protein footprinting approach to mapping DNA binding sites of two archael homing enzymes evidence for a two-domain protein structure. Nucleic Acids Res. 24, 3982-3989. 

The conformational space sampled by the two-domain protein calmodulin has been explored by an approach based on four sets of NMR observables obtained on Tb " and Tm -substituted proteins. The observables are the pseudocontact shifts and residual dipolar couplings of the C-terminal domain when lanthanide substitution is at the N-terminal domain. Each set of observables provides independent information on the conformations experienced by the molecule. It was found that not all sterically allowed conformations are equally populated. For example, taking the N-terminal domain as the reference, the C-terminal domain preferentially resides in a region of space inscribed in a wide elliptical cone. 

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