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Structural Insight into and Mutational Analysis of Family 11 Xylanases: Implications for Mechanisms of Higher pH Catalytic Adaptation.

Bai W, Zhou C, Zhao Y, Wang Q, Ma Y - PLoS ONE (2015)

Bottom Line: It was revealed that alkaline active xylanases have increased charged residue content, an increased ratio of negatively to positively charged residues, and decreased Ser, Thr, and Tyr residue content relative to non-alkaline active counterparts.Between strands β6 and β7, alkaline xylanases substitute an α-helix for a coil or turn found in their non-alkaline counterparts.By structure comparison, sequence alignment and mutational analysis, six amino acids (Glu16, Trp18, Asn44, Leu46, Arg48, and Ser187, numbering based on Xyn11A-LC) adjacent to the acid/base catalyst were found to be responsible for xylanase function in higher pH conditions.

View Article: PubMed Central - PubMed

Affiliation: National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, China; National Engineering Laboratory for Industrial Enzymes, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; School of Life Science, Shanxi Normal University, Linfen, 041004, China.

ABSTRACT
To understand the molecular basis of higher pH catalytic adaptation of family 11 xylanases, we compared the structures of alkaline, neutral, and acidic active xylanases and analyzed mutants of xylanase Xyn11A-LC from alkalophilic Bacillus sp. SN5. It was revealed that alkaline active xylanases have increased charged residue content, an increased ratio of negatively to positively charged residues, and decreased Ser, Thr, and Tyr residue content relative to non-alkaline active counterparts. Between strands β6 and β7, alkaline xylanases substitute an α-helix for a coil or turn found in their non-alkaline counterparts. Compared with non-alkaline xylanases, alkaline active enzymes have an inserted stretch of seven amino acids rich in charged residues, which may be beneficial for xylanase function in alkaline conditions. Positively charged residues on the molecular surface and ionic bonds may play important roles in higher pH catalytic adaptation of family 11 xylanases. By structure comparison, sequence alignment and mutational analysis, six amino acids (Glu16, Trp18, Asn44, Leu46, Arg48, and Ser187, numbering based on Xyn11A-LC) adjacent to the acid/base catalyst were found to be responsible for xylanase function in higher pH conditions. Our results will contribute to understanding the molecular mechanisms of higher pH catalytic adaptation in family 11 xylanases and engineering xylanases to suit industrial applications.

No MeSH data available.


Related in: MedlinePlus

Sequence alignment of family 11 mesophilic xylanases with known structure and pH-dependent activity.The boxed amino acids indicate the key residues to determine the pH activity profile.
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pone.0132834.g004: Sequence alignment of family 11 mesophilic xylanases with known structure and pH-dependent activity.The boxed amino acids indicate the key residues to determine the pH activity profile.

Mentions: Amino acid residues within a radius of 12 Å from either of the two catalytic amino acids were identified as residues that may play important roles in determining the optimal pHs of the homologous family 11 xylanases. Thirty-one residues adjacent to the two catalytic amino acids are not conserved among the alkaline xylanase 2DCK, the neutral xylanase 1XXN, and the acidophilic xylanase 1BK1. Sequence alignment of thirteen xylanases with different optimal pH and known structure shows that eight conserved residues within the alkaline group may be the key amino acids determining the pH optima of family 11 xylanases (Fig 4).


Structural Insight into and Mutational Analysis of Family 11 Xylanases: Implications for Mechanisms of Higher pH Catalytic Adaptation.

Bai W, Zhou C, Zhao Y, Wang Q, Ma Y - PLoS ONE (2015)

Sequence alignment of family 11 mesophilic xylanases with known structure and pH-dependent activity.The boxed amino acids indicate the key residues to determine the pH activity profile.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4498622&req=5

pone.0132834.g004: Sequence alignment of family 11 mesophilic xylanases with known structure and pH-dependent activity.The boxed amino acids indicate the key residues to determine the pH activity profile.
Mentions: Amino acid residues within a radius of 12 Å from either of the two catalytic amino acids were identified as residues that may play important roles in determining the optimal pHs of the homologous family 11 xylanases. Thirty-one residues adjacent to the two catalytic amino acids are not conserved among the alkaline xylanase 2DCK, the neutral xylanase 1XXN, and the acidophilic xylanase 1BK1. Sequence alignment of thirteen xylanases with different optimal pH and known structure shows that eight conserved residues within the alkaline group may be the key amino acids determining the pH optima of family 11 xylanases (Fig 4).

Bottom Line: It was revealed that alkaline active xylanases have increased charged residue content, an increased ratio of negatively to positively charged residues, and decreased Ser, Thr, and Tyr residue content relative to non-alkaline active counterparts.Between strands β6 and β7, alkaline xylanases substitute an α-helix for a coil or turn found in their non-alkaline counterparts.By structure comparison, sequence alignment and mutational analysis, six amino acids (Glu16, Trp18, Asn44, Leu46, Arg48, and Ser187, numbering based on Xyn11A-LC) adjacent to the acid/base catalyst were found to be responsible for xylanase function in higher pH conditions.

View Article: PubMed Central - PubMed

Affiliation: National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, China; National Engineering Laboratory for Industrial Enzymes, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; School of Life Science, Shanxi Normal University, Linfen, 041004, China.

ABSTRACT
To understand the molecular basis of higher pH catalytic adaptation of family 11 xylanases, we compared the structures of alkaline, neutral, and acidic active xylanases and analyzed mutants of xylanase Xyn11A-LC from alkalophilic Bacillus sp. SN5. It was revealed that alkaline active xylanases have increased charged residue content, an increased ratio of negatively to positively charged residues, and decreased Ser, Thr, and Tyr residue content relative to non-alkaline active counterparts. Between strands β6 and β7, alkaline xylanases substitute an α-helix for a coil or turn found in their non-alkaline counterparts. Compared with non-alkaline xylanases, alkaline active enzymes have an inserted stretch of seven amino acids rich in charged residues, which may be beneficial for xylanase function in alkaline conditions. Positively charged residues on the molecular surface and ionic bonds may play important roles in higher pH catalytic adaptation of family 11 xylanases. By structure comparison, sequence alignment and mutational analysis, six amino acids (Glu16, Trp18, Asn44, Leu46, Arg48, and Ser187, numbering based on Xyn11A-LC) adjacent to the acid/base catalyst were found to be responsible for xylanase function in higher pH conditions. Our results will contribute to understanding the molecular mechanisms of higher pH catalytic adaptation in family 11 xylanases and engineering xylanases to suit industrial applications.

No MeSH data available.


Related in: MedlinePlus