Structural highlights
FunctionPublication Abstract from PubMedThe membrane protein AtTLP18.3 contains a domain of unknown function, DUF477; it forms a polysome with photosynthetic apparatuses in the thylakoid lumen. To explore the molecular function of AtTLP18.3, we resolved its crystal structures with residues 83 to 260, the DUF477 only, and performed a series of biochemical analyses to discover its function. The gene expression of AtTLP18.3 followed a circadian rhythm. X-ray crystallography revealed the folding of AtTLP18.3 as a three-layer sandwich with 3 alpha-helices in the upper layer, 4 beta-sheets in the middle layer, and 2 alpha-helices in the lower layer, which resembles a Rossmann fold. Structural comparison suggested that AtTLP18.3 might be a phosphatase. The enzymatic activity of AtTLP18.3 was further confirmed by phosphatase assay with various substrates (e.g., p-nitrophenyl phosphate, 6,8 difluoro-4-methylumbelliferyl phosphate, O-phospho-L-Serine [pSer] and several synthetic phosphopeptides). Furthermore, we obtained the structure of AtTLP18.3 in complex with pSer to identify the binding site of AtTLP18.3. Our structural and biochemical studies revealed that AtTLP18.3 has a molecular function of a novel acid phosphatase in the thylakoid lumen. DUF477 is accordingly renamed the thylakoid acid phosphatase (TAP) domain. Structural and Functional Assays of AtTLP18.3 Identify Its Novel Acid Phosphatase Activity in Thylakoid Lumen.,Wu HY, Liu MS, Lin TP, Cheng YS Plant Physiol. 2011 Sep 9. PMID:21908686[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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