Crystal Structure of Okadaic Acid Binding Protein 2.1: A Sponge Protein Implicated in Cytotoxin Accumulation

Haruhiko Ehara, Marie Makino, Koichiro Kodama, Keiichi Konoki, Takuhiro Ito, Shun Ichi Sekine, Seketsu Fukuzawa, Shigeyuki Yokoyama, Kazuo Tachibana

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Okadaic acid (OA) is a marine polyether cytotoxin that was first isolated from the marine sponge Halichondria okadai. OA is a potent inhibitor of protein serine/threonine phosphatases (PP) 1 and 2A, and the structural basis of phosphatase inhibition has been well investigated. However, the role and mechanism of OA retention in the marine sponge have remained elusive. We have solved the crystal structure of okadaic acid binding protein 2.1 (OABP2.1) isolated from H. okadai; it has strong affinity for OA and limited sequence homology to other proteins. The structure revealed that OABP2.1 consists of two α-helical domains, with the OA molecule deeply buried inside the protein. In addition, the global fold of OABP2.1 was unexpectedly similar to that of aequorin, a jellyfish photoprotein. The presence of structural homologues suggested that, by using similar protein scaffolds, marine invertebrates have developed diverse survival systems adapted to their living environments.

Original languageEnglish
Pages (from-to)1435-1439
Number of pages5
Issue number10
Publication statusPublished - 2015 Jul 1


  • marine cytotoxins
  • okadaic acid
  • protein structure
  • sponges

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Organic Chemistry

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