Solution structure of microtubule-associated protein light chain 3 and identification of its functional subdomains.
Microtubule-associated protein (MAP) light chain 3 (LC3) is a human homologue of yeast Apg8/Aut7/Cvt5 (Atg8), which is essential for autophagy. MAP-LC3 is cleaved by a cysteine protease to produce LC3-I, which is located in cytosolic fraction. LC3-I, in turn, is converted to LC3-II through the actions of E1- and E2-like enzymes. LC3-II is covalently attached to phosphatidylethanolamine on its C terminus, and it binds tightly to autophagosome membranes. We determined the solution structure of LC3-I and found that it is divided into N- and C-terminal subdomains. Additional analysis using a photochemically induced dynamic nuclear polarization technique also showed that the N-terminal subdomain of LC3-I makes contact with the surface of the C-terminal subdomain and that LC3-I adopts a single compact conformation in solution. Moreover, the addition of dodecylphosphocholine into the LC3-I solution induced chemical shift perturbations primarily in the C-terminal subdomain, which implies that the two subdomains have different sensitivities to dodecylphosphocholine micelles. On the other hand, deletion of the N-terminal subdomain abolished binding of tubulin and microtubules. Thus, we showed that two subdomains of the LC3-I structure have distinct functions, suggesting that MAP-LC3 can act as an adaptor protein between microtubules and autophagosomes.
Kouno
Takahide
T
Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Toyama 930-0194, Japan.
Mizuguchi
Mineyuki
M
Tanida
Isei
I
Ueno
Takashi
T
Kanematsu
Takashi
T
Mori
Yoshihiro
Y
Shinoda
Hiroyuki
H
Hirata
Masato
M
Kominami
Eiki
E
Kawano
Keiichi
K
D001343:Autophagy; D003545:Cysteine / Q000737:chemistry; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D017353:Gene Deletion; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008869:Microtubule-Associated Proteins / Q000737:chemistry*; D008870:Microtubules / Q000737:chemistry; D008958:Models, Molecular; D009154:Mutation; D010587:Phagocytosis; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D020349:Surface Plasmon Resonance
C477012:MAP1LC3A protein, human; C502070:MAP1LC3B protein, human; C502071:MAP1LC3C protein, human; D008869:Microtubule-Associated Proteins; D010714:Phosphatidylethanolamines; D011994:Recombinant Proteins; D010767:Phosphorylcholine; C483858:phosphatidylethanolamine; C028810:dodecylphosphocholine; D003545:Cysteine