X-Ray Crystal Structure of the Full Length Human Chitotriosidase (CHIT1) Reveals Features of Its Chitin Binding Domain.
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.
Department of Integrative Biology, Institute of Genetics and Molecular and Cellular Biology (IGBMC), CNRS UMR 7104, INSERM U 964, Université de Strasbourg, Illkirch, France.
Firas
F
Fadel
Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, United Kingdom.
Yuguang
Y
Zhao
Department of Integrative Biology, Institute of Genetics and Molecular and Cellular Biology (IGBMC), CNRS UMR 7104, INSERM U 964, Université de Strasbourg, Illkirch, France.
Alexandra
A
Cousido-Siah
Department of Integrative Biology, Institute of Genetics and Molecular and Cellular Biology (IGBMC), CNRS UMR 7104, INSERM U 964, Université de Strasbourg, Illkirch, France.
Francesc X
FX
Ruiz
Department of Integrative Biology, Institute of Genetics and Molecular and Cellular Biology (IGBMC), CNRS UMR 7104, INSERM U 964, Université de Strasbourg, Illkirch, France.
André
A
Mitschler
Department of Integrative Biology, Institute of Genetics and Molecular and Cellular Biology (IGBMC), CNRS UMR 7104, INSERM U 964, Université de Strasbourg, Illkirch, France.
Alberto
A
Podjarny
D000485:Allergens / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001798:Blood Proteins / Q000737:chemistry / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D020134:Catalytic Domain; D002686:Chitin / Q000737:chemistry* / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry* / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry / Q000378:metabolism; D015870:Gene Expression; D057809:HEK293 Cells; D006596:Hexosaminidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D039981:Pyroglyphidae / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D013379:Substrate Specificity
D000485:Allergens; D001798:Blood Proteins; D002352:Carrier Proteins; D004220:Disulfides; D011994:Recombinant Proteins; C104989:tachycitin protein, Tachypleus tridentatus; D002686:Chitin; D006596:Hexosaminidases; C086400:chitotriosidase; D003545:Cysteine