 |
|
|
 |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
602 a.a.
_CA
Key reference
DOI no: 10.1021/bi030202i Biochemistry 43:1163-1170 (2004) PubMed id: 14756552
Structural basis for the exocellulase activity of the cellobiohydrolase CbhA from Clostridium thermocellum. F.D.Schubot, I.A.Kataeva, J.Chang, A.K.Shah, L.G.Ljungdahl, J.P.Rose, B.C.Wang. ABSTRACT
Numerous bacterial and fungal organisms have evolved elaborate sets of modular glycoside hydrolases and similar enzymes aimed at the degradation of polymeric carbohydrates. Presently, on the basis of sequence similarity catalytic modules of these enzymes have been classified into 90 families. Representatives of a particular family display similar fold and catalytic mechanisms. However, within families distinctions occur with regard to enzymatic properties and type of activity against carbohydrate chains. Cellobiohydrolase CbhA from Clostridium thermocellum is a large seven-modular enzyme with a catalytic module belonging to family 9. In contrast to other representatives of that family possessing only endo- and, in few cases, endo/exo-cellulase activities, CbhA is exclusively an exocellulase. The crystal structures of the combination of the immunoglobulin-like module and the catalytic module of CbhA (Ig-GH9_CbhA) and that of an inactive mutant Ig-GH9_CbhA(E795Q) in complex with cellotetraose (CTT) are reported here. The detailed analysis of these structures reveals that, while key catalytic residues and overall fold are conserved in this enzyme and those of other family 9 glycoside hydrolases, the active site of GH9_CbhA is blocked off after the -2 subsite. This feature which is created by an extension and altered conformation of a single loop region explains the inability of the active site of CbhA to accommodate a long cellulose chain and to cut it internally. This altered loop region is responsible for the exocellulolytic activity of the enzyme.
Literature references that cite this PDB file's key reference
PubMed id Reference
19622857 J.H.Pereira, R.Sapra, J.V.Volponi, C.L.Kozina, B.Simmons, and P.D.Adams (2009).
Structure of endoglucanase Cel9A from the thermoacidophilic Alicyclobacillus acidocaldarius.Acta Crystallogr D Biol Crystallogr, 65, 744-750.
PDB code: 3ez8
18203823 M.Qi, H.S.Jun, and C.W.Forsberg (2008).
Cel9D, an atypical 1,4-beta-D-glucan glucohydrolase from Fibrobacter succinogenes: characteristics, catalytic residues, and synergistic interactions with other cellulases.J Bacteriol, 190, 1976-1984.
17570146 B.Audit, E.D.Levy, W.R.Gilks, L.Goldovsky, and C.A.Ouzounis (2007).
CORRIE: enzyme sequence annotation with confidence estimates.BMC Bioinformatics, 8, S3.
17192265 W.S.Jung, C.K.Hong, S.Lee, C.S.Kim, S.J.Kim, S.I.Kim, and S.Rhee (2007).
Structural and functional insights into intramolecular fructosyl transfer by inulin fructotransferase.J Biol Chem, 282, 8414-8423.
PDB codes: 2inu 2inv
16384918 J.J.Adams, G.Pal, Z.Jia, and S.P.Smith (2006).
Mechanism of bacterial cell-surface attachment revealed by the structure of cellulosomal type II cohesin-dockerin complex.Proc Natl Acad Sci U S A, 103, 305-310.
PDB code: 2b59
16301798 Z.Q.Fu (2005).
Three-dimensional model-free experimental error correction of protein crystal diffraction data with free-R test.Acta Crystallogr D Biol Crystallogr, 61, 1643-1648. 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.
