Enhanced processive cellulases
Nucleic acid sequences encoding chimeric polypeptides that exhibit enhanced cellulase activities are disclosed herein. These nucleic acids may be expressed in hosts such as fungi, which in turn may be cultured to produce chimeric polypeptides. Also disclosed are chimeric polypeptides and their use in the degradation of cellulosic materials.
1. An isolated nucleic acid molecule encoding a chimeric fungal CeI7A polypeptide that has a cellulase activity at least 1.5-fold greater than the wild-type CeI7A polypeptide, wherein the chimeric CeI7A polypeptide comprises the following domains: a catalytic domain (CD), a carbohydrate-binding module (CBM) and a linker domain, and wherein at least one of the domains is from a Penicillium funiculosum CeI7A polypeptide and at least one of the domains is from a Trichoderma reesei CeI7A polypeptide; and wherein each domain is from the Penicillium funiculosum or Trichoderma reesei CeI7A polypeptides.
2. The isolated nucleic acid molecule of claim 1 , wherein the chimeric CeI7A polypeptide comprises the catalytic domain (CD) from the Penicillium funiculosum CeI7A polypeptide.
3. The isolated nucleic acid molecule of claim 2 , wherein the chimeric CeI7A polypeptide further comprises the carbohydrate-binding module (CBM) from the Trichoderma reesei CeI7A polypeptide.
4. The isolated nucleic acid molecule of claim 3 , wherein the chimeric CeI7A polypeptide further comprises the linker domain from the Penicillium funiculosum CeI7A polypeptide.
5. The isolated nucleic acid molecule of claim 1 , wherein the chimeric CeI7A polypeptide comprises the carbohydrate-binding module (CBM) from the Trichoderma reesei CeI7A polypeptide.
6. The isolated nucleic acid molecule of claim 1 , wherein the chimeric CeI7A polypeptide has the amino acid sequence of SEQ ID NOS:6, 8, 10, 12, 14 or 16.
7. The isolated nucleic acid molecule of claim 1 , wherein the nucleic acid molecule has the sequence of SEQ ID NOS:5, 7, 9, 11, 13 or 15.
8. The isolated nucleic acid molecule of claim 1 , further comprising a promoter operably linked to the nucleic acid molecule.
9. The isolated nucleic acid molecule of claim 8 , wherein the promoter allows expression of the nucleic acid in a filamentous fungal host cell.
10. An expression vector comprising the nucleic acid molecule of claim 1 .
11. A host cell comprising the expression vector of claim 10 or expressing a recombinant polypeptide encoded by the nucleic acid molecule of claim 1 .
12. The host cell of claim 11 , wherein the cell is a fungal cell.
13. The host cell of claim 12 , wherein the cell is from a strain of Trichoderma reesei.
14. The isolated nucleic acid molecule of claim 2 , wherein the chimeric CeI7A polypeptide further comprises the linker domain from the Trichoderma reesei CeI7A polypeptide.
15. The isolated nucleic acid molecule of claim 14 , wherein the chimeric CeI7A polypeptide further comprises the carbohydrate-binding module (CBM) from the Penicillium funiculosum CeI7A polypeptide.
16. The isolated nucleic acid molecule of claim 1 , wherein the chimeric CeI7A polypeptide comprises the catalytic domain (CD) from the Trichoderma reesei CeI7A polypeptide.
17. The isolated nucleic acid molecule of claim 16 , wherein the chimeric CeI7A polypeptide further comprises the linker domain from the Penicillium funiculosum CeI7A polypeptide.
18. The isolated nucleic acid molecule of claim 17 , wherein the chimeric CeI7A polypeptide further comprises the carbohydrate-binding module (CBM) from the Penicillium funiculosum CeI7A polypeptide.
19. The isolated nucleic acid molecule of claim 1 , wherein the chimeric fungal CeI7A polypeptide has a cellulase activity at least 2-fold greater than the wild-type CeI7A polypeptide.