TY - JOUR
T1 - Structural basis for polyglutamate chain initiation and elongation by TTLL family enzymes
AU - Mahalingan, Kishore K.
AU - Keith Keenan, E.
AU - Strickland, Madeleine
AU - Li, Yan
AU - Liu, Yanjie
AU - Ball, Haydn L.
AU - Tanner, Martin E.
AU - Tjandra, Nico
AU - Roll-Mecak, Antonina
N1 - Publisher Copyright:
© 2020, This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.
PY - 2020/9/1
Y1 - 2020/9/1
N2 - Glutamylation, introduced by tubulin tyrosine ligase-like (TTLL) enzymes, is the most abundant modification of brain tubulin. Essential effector proteins read the tubulin glutamylation pattern, and its misregulation causes neurodegeneration. TTLL glutamylases post-translationally add glutamates to internal glutamates in tubulin carboxy-terminal tails (branch initiation, through an isopeptide bond), and additional glutamates can extend these (elongation). TTLLs are thought to specialize in initiation or elongation, but the mechanistic basis for regioselectivity is unknown. We present cocrystal structures of murine TTLL6 bound to tetrahedral intermediate analogs that delineate key active-site residues that make this enzyme an elongase. We show that TTLL4 is exclusively an initiase and, through combined structural and phylogenetic analyses, engineer TTLL6 into a branch-initiating enzyme. TTLL glycylases add glycines post-translationally to internal glutamates, and we find that the same active-site residues discriminate between initiase and elongase glycylases. These active-site specializations of TTLL glutamylases and glycylases ultimately yield the chemical complexity of cellular microtubules.
AB - Glutamylation, introduced by tubulin tyrosine ligase-like (TTLL) enzymes, is the most abundant modification of brain tubulin. Essential effector proteins read the tubulin glutamylation pattern, and its misregulation causes neurodegeneration. TTLL glutamylases post-translationally add glutamates to internal glutamates in tubulin carboxy-terminal tails (branch initiation, through an isopeptide bond), and additional glutamates can extend these (elongation). TTLLs are thought to specialize in initiation or elongation, but the mechanistic basis for regioselectivity is unknown. We present cocrystal structures of murine TTLL6 bound to tetrahedral intermediate analogs that delineate key active-site residues that make this enzyme an elongase. We show that TTLL4 is exclusively an initiase and, through combined structural and phylogenetic analyses, engineer TTLL6 into a branch-initiating enzyme. TTLL glycylases add glycines post-translationally to internal glutamates, and we find that the same active-site residues discriminate between initiase and elongase glycylases. These active-site specializations of TTLL glutamylases and glycylases ultimately yield the chemical complexity of cellular microtubules.
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U2 - 10.1038/s41594-020-0462-0
DO - 10.1038/s41594-020-0462-0
M3 - Article
C2 - 32747782
AN - SCOPUS:85088862511
SN - 1545-9993
VL - 27
SP - 802
EP - 813
JO - Nature Structural and Molecular Biology
JF - Nature Structural and Molecular Biology
IS - 9
ER -