Structure of GATE-16, Membrane Transport Modulator and Mammalian Ortholog of Autophagocytosis Factor Aut7p

Abstract

The GATE-16 protein participates in intra-Golgi transport and can associate with the N-ethylmaleimide-sensitive fusion protein and with Golgi SNAREs. The yeast ortholog of GATE-16 is the autophagocytosis factor Aut7p. GATE-16 is also closely related to the GABA receptor-associated protein (GABARAP), which has been proposed to cluster neurotransmitter receptors by mediating interaction with the cytoskeleton, and to the light chain-3 subunit of the neuronal microtubule-associated protein complex. Here, we present the crystal structure of GATE-16 refined to 1.8 Å resolution. GATE-16 contains a ubiquitin fold decorated by two additional N-terminal helices. Proteins with strong structural similarity but no detectable sequence homology to GATE-16 include Ras effectors that mediate diverse downstream functions, but each interacts with Ras by forming pseudo-continuous ␤-sheets. The GATE-16 surface suggests that it binds its targets in a similar manner. Moreover, a second potential protein-protein interaction site on GATE-16 may explain the adapter activity observed for members of the GATE-16 family.

GABARAPL1 (GEC1): Original or copycat?

“…1). GABARAPL1 shows 87% identity with GABARAP and 61% identity with GATE-16 5,6 and also shares a distant homology with LC3A (30.8% identity), LC3B (29% identity) and LC3C (35.8% identity). [7][8][9][10] Members of the GABARAP and LC3 families are composed of 117 to 145 amino acids and all possess a conserved C-terminal glycine, essential for their role in autophagy (Fig.…”

“…1). 11,12 In addition to their sequence similarity, the crystal structures of GABARAP, [13][14][15][16][17] GATE-16, 6 LC3, 18 and…”

SUMO: of branched proteins and nuclear bodies

“…In all ®ve, the modi®cation reaction is carried out in distinct pathways that are analogous to ubiquitylation, and further, all ®ve modi®ers are structurally related to ubiquitin. Indeed, although Apg8p/Aut7p displays almost no primary sequence homology to ubiquitin, the recent Xray structure determination of its mammalian ortholog GATE-16 did reveal the ubiquitin fold structure (Paz et al, 2000). It is thus tempting to speculate that there may be (numerous?)…”

The COOH Terminus of GATE-16, an Intra-Golgi Transport Modulator, Is Cleaved by the Human Cysteine Protease HsApg4A

“…GATE-16 is recruited to unpaired GOS-28, a Golgi-specific SNARE, in an NSF/␣-SNAP-dependent manner (7,8), thus preventing GOS-28 from interacting with its cognate t-SNARE syntaxin 5. As was determined by its crystal structure (9), GATE-16 contains a ubiquitin fold decorated by two additional NH 2 -terminal helices. GATE-16 belongs to the ubiquitin-like protein family and shares a high level of sequence identity with an expanding family of proteins that have been implicated in a variety of cellular processes.…”