PDBsum entry 4ipm

Hydrolase

PDB id: 4ipm

Contents

Protein chain

431 a.a.

Ligands

SGC-BGC

ACT

Metals

_CA

Waters ×687

PDB id:

4ipm

Name:

Hydrolase

Title:

Crystal structure of a gh7 family cellobiohydrolase from limnoria quadripunctata in complex with thiocellobiose

Structure:

Gh7 family protein. Chain: a. Fragment: unp residues 19-448. Engineered: yes

Source:

Limnoria quadripunctata. Organism_taxid: 161573. Gene: gh7b. Expressed in: aspergillus oryzae. Expression_system_taxid: 5062

Resolution:

1.14Å R-factor: 0.123 R-free: 0.155

Authors:

J.E.Mcgeehan,R.N.A.Martin,S.D.Streeter,S.M.Cragg,M.J.Guille, K.M.Schnorr,M.Kern,N.C.Bruce,S.J.Mcqueen-Mason

Key ref:

M.Kern et al. (2013). Structural characterization of a unique marine animal family 7 cellobiohydrolase suggests a mechanism of cellulase salt tolerance. Proc Natl Acad Sci U S A, 110, 10189-10194. PubMed id: 23733951 DOI: 10.1073/pnas.1301502110

Date:

10-Jan-13 Release date: 12-Jun-13

Protein chain

D4HRL0  (GH7B_LIMQU) -  Exoglucanase GH7B from Limnoria quadripunctata

Seq: 448 a.a.

Struc: 431 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.3.2.1.91 - cellulose 1,4-beta-cellobiosidase (non-reducing end).
• Reaction: Hydrolysis of 1,4-beta-D-glucosidic linkages in cellulose and cellotetraose, releasing cellobiose from the non-reducing ends of the chains.

DOI no: 10.1073/pnas.1301502110

Proc Natl Acad Sci U S A 110:10189-10194 (2013)

PubMed id: 23733951

Structural characterization of a unique marine animal family 7 cellobiohydrolase suggests a mechanism of cellulase salt tolerance.

M.Kern, J.E.McGeehan, S.D.Streeter, R.N.Martin, K.Besser, L.Elias, W.Eborall, G.P.Malyon, C.M.Payne, M.E.Himmel, K.Schnorr, G.T.Beckham, S.M.Cragg, N.C.Bruce, S.J.McQueen-Mason.

ABSTRACT

Nature uses a diversity of glycoside hydrolase (GH) enzymes to convert polysaccharides to sugars. As lignocellulosic biomass deconstruction for biofuel production remains costly, natural GH diversity offers a starting point for developing industrial enzymes, and fungal GH family 7 (GH7) cellobiohydrolases, in particular, provide significant hydrolytic potential in industrial mixtures. Recently, GH7 enzymes have been found in other kingdoms of life besides fungi, including in animals and protists. Here, we describe the in vivo spatial expression distribution, properties, and structure of a unique endogenous GH7 cellulase from an animal, the marine wood borer Limnoria quadripunctata (LqCel7B). RT-quantitative PCR and Western blot studies show that LqCel7B is expressed in the hepatopancreas and secreted into the gut for wood degradation. We produced recombinant LqCel7B, with which we demonstrate that LqCel7B is a cellobiohydrolase and obtained four high-resolution crystal structures. Based on a crystallographic and computational comparison of LqCel7B to the well-characterized Hypocrea jecorina GH7 cellobiohydrolase, LqCel7B exhibits an extended substrate-binding motif at the tunnel entrance, which may aid in substrate acquisition and processivity. Interestingly, LqCel7B exhibits striking surface charges relative to fungal GH7 enzymes, which likely results from evolution in marine environments. We demonstrate that LqCel7B stability and activity remain unchanged, or increase at high salt concentration, and that the L. quadripunctata GH mixture generally contains cellulolytic enzymes with highly acidic surface charge compared with enzymes derived from terrestrial microbes. Overall, this study suggests that marine cellulases offer significant potential for utilization in high-solids industrial biomass conversion processes.