Solution structure of the catalytic domain of RICH protein from goldfish

• Published in: The FEBS journal Vol. 274; no. 6; pp. 1600 - 1609
• Main Authors: Kozlov, Guennadi, Denisov, Alexey Y., Pomerantseva, Ekaterina, Gravel, Michel, Braun, Peter E., Gehring, Kalle
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.03.2007
• Subjects: 2H phosphoesterase superfamily; Amino Acid Sequence; Animals; Binding sites; Biochemistry; Carassius auratus; Catalysis; Catalytic Domain; CNPase; Crystal structure; Fish; Freshwater; Goldfish; Models, Molecular; Molecular Sequence Data; Nerve Tissue Proteins - chemistry; NMR; NMR solution structure; Nuclear magnetic resonance; Nuclear Magnetic Resonance, Biomolecular; Protein Conformation; Proteins; RICH protein; Sequence Homology, Amino Acid; Teleostei; tRNA splicing
• ISSN: 1742-464X; 1742-4658
• DOI: 10.1111/j.1742-4658.2007.05707.x

Regeneration‐induced CNPase homolog (RICH) is an axonal growth‐associated protein, which is induced in teleost fish upon optical nerve injury. RICH consists of a highly acidic N‐terminal domain, a catalytic domain with 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase (CNPase) activity and a C‐terminal isoprenylation site. In vitro RICH and mammalian brain CNPase specifically catalyze the hydrolysis of 2′,3′‐cyclic nucleotides to produce 2′‐nucleotides, but the physiologically relevant in vivo substrate remains unknown. Here, we report the NMR structure of the catalytic domain of goldfish RICH and describe its binding to CNPase inhibitors. The structure consists of a twisted nine‐stranded antiparallel β‐sheet surrounded by α‐helices on both sides. Despite significant local differences mostly arising from a seven‐residue insert in the RICH sequence, the active site region is highly similar to that of human CNPase. Likewise, refinement of the catalytic domain of rat CNPase using residual dipolar couplings gave improved agreement with the published crystal structure. NMR titrations of RICH with inhibitors point to a similar catalytic mechanism for RICH and CNPase. The results suggest a functional importance for the evolutionarily conserved phosphodiesterase activity and hint of a link with pre‐tRNA splicing.