Scallop lens O-crystallin (ALDH1A9): A novel tetrameric aldehyde dehydrogenase

Scallop lens O-crystallin (ALDH1A9): A novel tetrameric aldehyde dehydrogenase
Received 27 July 2006. Available online 8 August 2006.
Joseph Horwitza, Linlin Dinga, Vasilis Vasilioub, Miriam Cantoreb and Joram Piatigorskyc
Biochemical and Biophysical Research Communications
Volume 348, Issue 4 , 6 October 2006
Published by Elsevier Inc.
aJules Stein Eye Institute, UCLA School of Medicine, Los Angeles, CA 90095-7008, USA
bMolecular Toxicology and Environmental Health Sciences Program, Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, CO 80262, USA
cNational Eye Institute, Laboratory of Molecular and Developmental Biology, Bethesda, MD 20892-0704, USA
Scallop eye lens O-crystallin is an inactive aldehyde dehydrogenase (ALDH1A9) related to cytoplasmic ALDH1A1 and mitochondrial ALDH2 that migrates by gel filtration chromatography as a homodimer. Because mammalian ALDH1A1 and ALDH2 are homotetramers, we investigated the native molecular mass of scallop O-crystallin by multi-angle laser light scattering. The results indicate that the scallop O-crystallin is a tetrameric, not a dimeric protein. Moreover, phylogenetic tree analysis shows that scallop O-crystallin clusters with the mitochondrial ALDH2 and ALDH1B1 rather than the cytoplasmic ALDH1A, yet it lacks the mitochondrial N-terminal leader sequence characteristic of the mitochondrial ALDHs. The mitochondrial grouping, enzymatic inactivity, and anomalous gel filtration behavior make scallop cytoplasmic O-crystallin an interesting protein for structural studies of evolutionary adaptations to become an enzyme-crystallin.
Keywords: Lens crystallin; Scallop; O-crystallin; Aldehyde dehydrogenase; Molecular mass; Multi-angle laser light scattering; Mitochondria

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