Residual domains

CDK2 has two domains, a small (85 residue) amino-terminal domain comprising a single a helix and a five-stranded p sheet and a larger (213 residues) domain that is mainly a-helical (Figure 6.17a). The cofactor in the... 

Del Vecchio, F., Petkovic, H., Kendrew, S.G. et al. (2003) Active-site residue, domain and module swaps in modular polyketide synthases. Journal of Industrial Microbiology Biotechnology, 30, 489. 

The last major category (shown in Figs. 85 and 86) consists of small (usually less than 100 residues) domains whose structures seem to be strongly influenced by their high content either of disulfide bonds (S)... 

The largest /f-bar re Is have been observed with the monomeric iron transporter proteins FhuA and FepA. The structure of FhuA was established independently by two groups (Locher et al., 1998 Ferguson et al., 1998). It is known with and without a ligated siderophore. The structure of the ferric enterobactin receptor FepA is homologous to that of FhuA showing identical topology and a similar transport mechanism (Buchanan etal., 1999). In both cases there are more than 700 residues assembled in two domains an N-terminal 150-residue domain is located inside a C-terminal 22-stranded (6-barrel with a shear number S = 24. 

Channels are of course also formed by all porins. A general porin contains 16 /1-strands and has a shear number of 20 and a nearly circular cross section (Table II). Three parallel barrels associate to form trimers. The type of residues outlining the channel determines the specificity of a porin which, however, is usually not very strict. The two 18-stranded porins are very specific. Their channel cross-sections are actually smaller than those of the general porins in agreement with their higher selectivity. The 22-stranded barrels of the iron transporter proteins have circular cross sections and would form a very wide channel if they were not filled with the globular N-terminal 150-residue domain. 

Del Vecchio F, Petkovic H, Kendrew SG, Low L, Wilkinson B, Lill R, Cortes J, Rudd BA, Staunton J, Leadlay PF (2003) Active-Site Residue, Domain and Module Swaps in Modular Polyketide Synthases. J Ind Microbiol Biotechnol 30 489... 

A second domain is necessary for binding to subunits Ej and Eg, while the third major 250-residue domain contains the catalytic acyltransferase center.3 3 309 center closely resembles that of chloramphenicol acetyl-transferase (Qiapter I2).3i0/3ii jj g jjpgyj30i.309.3i2... 

Receptor residues/domains critical for G protein coupling selectivity... 

This class of peptides typically contains 18 or 19 amino acid residues and share a common 13 amino acid sequence, which is Cys -Cys-Glu-Leu-Cys-Cys °-Asn-Pro-Ala-Cys-Ala -Gly-Cys (full peptide position) and Cys -Cys-Glu-Leu-Cys-Cys -Asn-Pro-Ala-Cys-Ala -Gly-Cys (toxic domain). Since the domain is conserved in several enterotoxins, one expects this 13 residue domain to be the primary reason for the toxicity. The six Cys residues form three disulphide bridges, and provide stability to the structure of the protein. lETN has a simple structure it has got three beta ((3) turns. In addition, the crystal structure contains five intramolecular hydrogen bonds that also add to the stability of the protein. Another interesting aspect of this protein is the presence of 13 water molecules in the crystal structure (Sato et al., 1986). Overall, this protein has a hydrophobic character, as the side chains of all residues are oriented to the outside of the molecule (Balasubramanian et al., 2003). 

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