X-Ray Crystal Structure of the Full Length Human Chitotriosidase (CHIT1) Reveals Features of Its Chitin Binding Domain

PLoS One. 2016 Apr 25;11(4):e0154190. doi: 10.1371/journal.pone.0154190. eCollection 2016.

Abstract

Chitinases are enzymes that catalyze the hydrolysis of chitin. Human chitotriosidase (CHIT1) is one of the two active human chitinases, involved in the innate immune response and highly expressed in a variety of diseases. CHIT1 is composed of a catalytic domain linked by a hinge to its chitin binding domain (ChBD). This latter domain belongs to the carbohydrate-binding module family 14 (CBM14 family) and facilitates binding to chitin. So far, the available crystal structures of the human chitinase CHIT1 and the Acidic Mammalian Chitinase (AMCase) comprise only their catalytic domain. Here, we report a crystallization strategy combining cross-seeding and micro-seeding cycles which allowed us to obtain the first crystal structure of the full length CHIT1 (CHIT1-FL) at 1.95 Å resolution. The CHIT1 chitin binding domain (ChBDCHIT1) structure shows a distorted β-sandwich 3D fold, typical of CBM14 family members. Accordingly, ChBDCHIT1 presents six conserved cysteine residues forming three disulfide bridges and several exposed aromatic residues that probably are involved in chitin binding, including the highly conserved Trp465 in a surface- exposed conformation. Furthermore, ChBDCHIT1 presents a positively charged surface which may be involved in electrostatic interactions. Our data highlight the strong structural conservation of CBM14 family members and uncover the structural similarity between the human ChBDCHIT1, tachycitin and house mite dust allergens. Overall, our new CHIT1-FL structure, determined with an adapted crystallization approach, is one of the few complete bi-modular chitinase structures available and reveals the structural features of a human CBM14 domain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allergens / chemistry
  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Blood Proteins / chemistry
  • Blood Proteins / metabolism
  • Carrier Proteins / chemistry
  • Carrier Proteins / metabolism
  • Catalytic Domain
  • Chitin / chemistry*
  • Chitin / metabolism
  • Cysteine / chemistry*
  • Cysteine / metabolism
  • Disulfides / chemistry
  • Disulfides / metabolism
  • Gene Expression
  • HEK293 Cells
  • Hexosaminidases / chemistry*
  • Hexosaminidases / genetics
  • Hexosaminidases / metabolism
  • Humans
  • Models, Molecular
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Structure, Secondary
  • Pyroglyphidae / chemistry
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Static Electricity
  • Substrate Specificity

Substances

  • Allergens
  • Blood Proteins
  • Carrier Proteins
  • Disulfides
  • Recombinant Proteins
  • tachycitin protein, Tachypleus tridentatus
  • Chitin
  • Hexosaminidases
  • chitotriosidase
  • Cysteine

Grant support

This work has been supported by the CNRS, the INSERM, the Université de Strasbourg. The authors wish to acknowledge the following grant funding: Biostruct-X (FP7, contract 283570, http://www.biostruct-x.eu/), and the French Infrastructure for Integrated Structural Biology (FRISBI, ANR-10-INSB-05-01, http://frisbi.eu/).