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Logo of jbcThe Journal of Biological Chemistry
J Biol Chem. 2012 November 30; 287(49): 41405.
PMCID: PMC3510838

Protein Acetyltransferase RpPat Demands Both a Motif and a Loop for Substrate Recognition♦

Structural Insights into the Substrate Specificity of the Rhodopseudomonas palustris Protein Acetyltransferase (RpPat). Identification of a Loop Critical for Recognition by RpPat

♦ See referenced article, J. Biol. Chem. 2012, 287, 41392–41404

Lysine acetylation is a critical post-translational modification for regulating metabolism in both prokaryotes and eukaryotes. In the purple photosynthetic bacterium Rhodopseudomonas palustris, at least 10 AMP-forming acyl-CoA synthetase enzymes are acetylated by a protein acetyltransferase called RpPat. The enzyme's substrates all contain the motif PX4GK. In this Paper of the Week, a team led by Jorge C. Escalante-Semerena at the University of Georgia showed that the motif was needed but not sufficient for recognition by RpPat. By studying chimeras of RpPat substrates in vitro and in vivo as well as analyzing their crystal structures, the investigators demonstrated that a surface region associated with a loop 23 Å from the acetylation site was also important for recognition. The authors concluded, “On the basis of these results, we suggest that RpPat likely interacts with a relatively large surface of its substrates, in addition to the PX4GK motif, and that RpPat probably has relatively narrow substrate specificity.”

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Stereo view of the accessibility of Lys-488 in the apo conformation of RpPat.

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