1v0a: Difference between revisions
From Proteopedia
Jump to navigationJump to search
No edit summary |
No edit summary |
||
| Line 5: | Line 5: | ||
==Overview== | ==Overview== | ||
Modular glycoside hydrolases that attack recalcitrant polymers generally, contain noncatalytic carbohydrate-binding modules (CBMs), which play a, critical role in the action of these enzymes by localizing the appended, catalytic domains onto the surface of insoluble polysaccharide substrates., Type B CBMs, which recognize single polysaccharide chains, display ligand, specificities that are consistent with the substrates hydrolyzed by the, associated catalytic domains. In enzymes that contain multiple catalytic, domains with distinct substrate specificities, it is unclear how these, different activities influence the evolution of the ligand recognition, profile of the appended CBM. To address this issue, we have characterized, the properties of a family 11 CBM (CtCBM11) in Clostridium ... | Modular glycoside hydrolases that attack recalcitrant polymers generally, contain noncatalytic carbohydrate-binding modules (CBMs), which play a, critical role in the action of these enzymes by localizing the appended, catalytic domains onto the surface of insoluble polysaccharide substrates., Type B CBMs, which recognize single polysaccharide chains, display ligand, specificities that are consistent with the substrates hydrolyzed by the, associated catalytic domains. In enzymes that contain multiple catalytic, domains with distinct substrate specificities, it is unclear how these, different activities influence the evolution of the ligand recognition, profile of the appended CBM. To address this issue, we have characterized, the properties of a family 11 CBM (CtCBM11) in Clostridium thermocellum, Lic26A-Cel5E, an enzyme that contains GH5 and GH26 catalytic domains that, display beta-1,4- and beta-1,3-1,4-mixed linked endoglucanase activity, respectively. Here we show that CtCBM11 binds to both beta-1,4- and, beta-1,3-1,4-mixed linked glucans, displaying K(a) values of 1.9 x 10(5), 4.4 x 10(4), and 2 x 10(3) m(-1) for, Glc-beta1,4-Glc-beta1,4-Glc-beta1,3-Glc, Glc-beta1,4-Glc-beta1,4-Glc-beta1,4-Glc, and, Glc-beta1,3-Glc-beta1,4-Glc-beta1,3-Glc, respectively, demonstrating that, CBMs can display a preference for mixed linked glucans. To determine, whether these ligands are accommodated in the same or diverse sites in, CtCBM11, the crystal structure of the protein was solved to a resolution, of 1.98 A. The protein displays a beta-sandwich with a concave side that, forms a potential binding cleft. Site-directed mutagenesis revealed that, Tyr(22), Tyr(53), and Tyr(129), located in the putative binding cleft, play a central role in the recognition of all the ligands recognized by, the protein. We propose, therefore, that CtCBM11 contains a single, ligand-binding site that displays affinity for both beta-1,4- and, beta-1,3-1,4-mixed linked glucans. | ||
==About this Structure== | ==About this Structure== | ||
1V0A is a | 1V0A is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Clostridium_thermocellum Clostridium thermocellum] with CA and SO4 as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Cellulase Cellulase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.4 3.2.1.4] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1V0A OCA]. | ||
==Reference== | ==Reference== | ||
| Line 33: | Line 33: | ||
[[Category: hydrolase]] | [[Category: hydrolase]] | ||
''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on | ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov 5 14:47:00 2007'' | ||
