Structural and functional characterization of the α-tubulin acetyltransferase MEC-17.
Tubulin protomers undergo an extensive array of post-translational modifications to tailor microtubules to specific tasks. One such modification, the acetylation of lysine 40 of α-tubulin, located in the lumen of microtubules, is associated with stable, long-living microtubule structures. MEC-17 was recently identified as the acetyltransferase that mediates this event. We have determined the crystal structure of the catalytic core of human MEC-17 in complex with its cofactor acetyl-CoA at 1.7Å resolution. The structure reveals that the MEC-17 core adopts a canonical Gcn5-related N-acetyltransferase (GNAT) fold that is decorated with extensive surface loops. An enzymatic analysis of 33 MEC-17 surface mutants identifies hot-spot residues for catalysis and substrate recognition. A large, evolutionarily conserved hydrophobic surface patch that is critical for enzymatic activity is identified, suggesting that specificity is achieved by interactions with the α-tubulin substrate that extend outside of the modified surface loop. An analysis of MEC-17 mutants in Caenorhabditis elegans shows that enzymatic activity is dispensable for touch sensitivity.
Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
Andrew M
AM
Davenport
Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
Leslie N
LN
Collins
Howard Hughes Medical Institute, Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
Hui
H
Chiu
Howard Hughes Medical Institute, Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
Paul J
PJ
Minor
Howard Hughes Medical Institute, Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA. Electronic address: pws@caltech.edu.
Paul W
PW
Sternberg
Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA. Electronic address: hoelz@caltech.edu.
André
A
Hoelz
D000105:Acetyl Coenzyme A / Q000737:chemistry / Q000378:metabolism; D000123:Acetyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008868:Microtubule Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014404:Tubulin / Q000378:metabolism
D029742:Caenorhabditis elegans Proteins; D008868:Microtubule Proteins; D011994:Recombinant Proteins; D014404:Tubulin; D000105:Acetyl Coenzyme A; D000123:Acetyltransferases; C000627069:ATAT1 protein, human; C049182:alpha-tubulin acetylase
C. elegans; X-ray crystallography; mechanosensation; substrate recognition; tubulin acetyltransferase