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Open Access Research article

Crystal structures of wild-type and mutated cyclophilin B that causes hyperelastosis cutis in the American quarter horse

Sergei P Boudko12, Yoshihiro Ishikawa12, Thomas F Lerch2, Jay Nix3, Michael S Chapman2 and Hans Peter Bächinger12*

Author Affiliations

1 Research Department, Shriners Hospital for Children, Portland, OR 97239, USA

2 Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, OR 97239, USA

3 Molecular Biology Consortium, Advanced Light Source Beamline 4.2.2, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA

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BMC Research Notes 2012, 5:626  doi:10.1186/1756-0500-5-626

Published: 8 November 2012



Hyperelastosis cutis is an inherited autosomal recessive connective tissue disorder. Affected horses are characterized by hyperextensible skin, scarring, and severe lesions along the back. The disorder is caused by a mutation in cyclophilin B.


The crystal structures of both wild-type and mutated (Gly6->Arg) horse cyclophilin B are presented. The mutation neither affects the overall fold of the enzyme nor impairs the catalytic site structure. Instead, it locally rearranges the flexible N-terminal end of the polypeptide chain and also makes it more rigid.


Interactions of the mutated cyclophilin B with a set of endoplasmic reticulum-resident proteins must be affected.

Peptidyl prolyl cis-trans-isomerase (PPIase); Cyclophilin B (CypB); Endoplasmic reticulum; Chaperone; Protein complex; Calreticulin; P-domain; Lysyl hydroxylase; Collagen; HERDA