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353 a.a.
_MG
Key reference
DOI no: 10.1110/ps.062220206 Protein Sci 15:1951-1960 (2006) PubMed id: 16823036
Crystal structures of native and xylosaccharide-bound alkali thermostable xylanase from an alkalophilic Bacillus sp. NG-27: structural insights into alkalophilicity and implications for adaptation to polyextreme conditions. K.Manikandan, A.Bhardwaj, N.Gupta, N.K.Lokanath, A.Ghosh, V.S.Reddy, S.Ramakumar. ABSTRACT
Crystal structures are known for several glycosyl hydrolase family 10 (GH10) xylanases. However, none of them is from an alkalophilic organism that can grow in alkaline conditions. We have determined the crystal structures at 2.2 Angstroms of a GH10 extracellular endoxylanase (BSX) from an alkalophilic Bacillus sp. NG-27, for the native and the complex enzyme with xylosaccharides. The industrially important enzyme is optimally active and stable at 343 K and at a pH of 8.4. Comparison of the structure of BSX with those of other thermostable GH10 xylanases optimally active at acidic or close to neutral pH showed that the solvent-exposed acidic amino acids, Asp and Glu, are markedly enhanced in BSX, while solvent-exposed Asn was noticeably depleted. The BSX crystal structure when compared with putative three-dimensional homology models of other extracellular alkalophilic GH10 xylanases from alkalophilic organisms suggests that a protein surface rich in acidic residues may be an important feature common to these alkali thermostable enzymes. A comparison of the surface features of BSX and of halophilic proteins allowed us to predict the activity of BSX at high salt concentrations, which we verified through experiments. This offered us important lessons in the polyextremophilicity of proteins, where understanding the structural features of a protein stable in one set of extreme conditions provided clues about the activity of the protein in other extreme conditions. The work brings to the fore the role of the nature and composition of solvent-exposed residues in the adaptation of enzymes to polyextreme conditions, as in BSX.
Literature references that cite this PDB file's key reference
PubMed id Reference
18725971 A.Bharadwaj, S.Leelavathi, S.Mazumdar-Leighton, A.Ghosh, S.Ramakumar, and V.S.Reddy (2008).
The critical role of partially exposed N-terminal valine residue in stabilizing GH10 xylanase from Bacillus sp.NG-27 under poly-extreme conditions.PLoS ONE, 3, e3063.
17642511 V.Solomon, A.Teplitsky, S.Shulami, G.Zolotnitsky, Y.Shoham, and G.Shoham (2007).
Structure-specificity relationships of an intracellular xylanase from Geobacillus stearothermophilus.Acta Crystallogr D Biol Crystallogr, 63, 845-859.
PDB code: 2q8x The most recent references are shown first. Citation data come partly from CiteXplore and partly from an automated harvesting procedure. Note that this is likely to be only a partial list as not all journals are covered by either method. However, we are continually building up the citation data so more and more references will be included with time. Where a reference describes a PDB structure, the PDB code is shown on the right.
