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2hxx

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{{STRUCTURE_2hxx| PDB=2hxx | SCENE= }}
{{STRUCTURE_2hxx| PDB=2hxx | SCENE= }}
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'''Aminotryptophan Barstar'''
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===Aminotryptophan Barstar===
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==Overview==
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The indole ring of the canonical amino acid tryptophan (Trp) possesses distinguished features, such as sterical bulk, hydrophobicity and the nitrogen atom which is capable of acting as a hydrogen bond donor. The introduction of an amino group into the indole moiety of Trp yields the structural analogs 4-aminotryptophan ((4-NH(2))Trp) and 5-aminotryptophan ((5-NH(2))Trp). Their hydrophobicity and spectral properties are substantially different when compared to those of Trp. They resemble the purine bases of DNA and share their capacity for pH-sensitive intramolecular charge transfer. The Trp --&gt; aminotryptophan substitution in proteins during ribosomal translation is expected to result in related protein variants that acquire these features. These expectations have been fulfilled by incorporating (4-NH(2))Trp and (5-NH(2))Trp into barstar, an intracellular inhibitor of the ribonuclease barnase from Bacillus amyloliquefaciens. The crystal structure of (4-NH(2))Trp-barstar is similar to that of the parent protein, whereas its spectral and thermodynamic behavior is found to be remarkably different. The T(m) value of (4-NH(2))Trp- and (5-NH(2))Trp-barstar is lowered by about 20 degrees Celsius, and they exhibit a strongly reduced unfolding cooperativity and substantial loss of free energy in folding. Furthermore, folding kinetic study of (4-NH(2))Trp-barstar revealed that the denatured state is even preferred over native one. The combination of structural and thermodynamic analyses clearly shows how structures of substituted barstar display a typical structure-function tradeoff: the acquirement of unique pH-sensitive charge transfer as a novel function is achieved at the expense of protein stability. These findings provide a new insight into the evolution of the amino acid repertoire of the universal genetic code and highlight possible problems regarding protein engineering and design by using an expanded genetic code.
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(as it appears on PubMed at http://www.pubmed.gov), where 16782415 is the PubMed ID number.
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{{ABSTRACT_PUBMED_16782415}}
==About this Structure==
==About this Structure==
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[[Category: Protein folding]]
[[Category: Protein folding]]
[[Category: Stability]]
[[Category: Stability]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 18:54:38 2008''

Revision as of 15:54, 28 July 2008

Image:2hxx.png

Template:STRUCTURE 2hxx

Aminotryptophan Barstar

Template:ABSTRACT PUBMED 16782415

About this Structure

2HXX is a Single protein structure of sequence from Bacillus amyloliquefaciens. Full crystallographic information is available from OCA.

Reference

Aminotryptophan-containing barstar: structure--function tradeoff in protein design and engineering with an expanded genetic code., Rubini M, Lepthien S, Golbik R, Budisa N, Biochim Biophys Acta. 2006 Jul;1764(7):1147-58. Epub 2006 May 10. PMID:16782415

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