Oct 25, 2018

N-terminal β-strand underpins biochemical specialization of an ATG8 isoform

BioRxiv : the Preprint Server for Biology
Erin K ZessYasin Dagdas

Abstract

ATG8 is a highly-conserved ubiquitin-like protein that modulates autophagy pathways by binding autophagic membranes and numerous proteins, including cargo receptors and core autophagy components. Throughout plant evolution, ATG8 has expanded from a single protein in algae to multiple isoforms in higher plants. However, the degree to which ATG8 isoforms have functionally specialized to bind distinct proteins remains unclear. Here, we describe a comprehensive protein-protein interaction resource, obtained using in planta immunoprecipitation followed by mass spectrometry, to define the potato ATG8 interactome. We discovered that ATG8 isoforms bind distinct sets of plant proteins with varying degrees of overlap. This prompted us to define the biochemical basis of ATG8 specialization by comparing two potato ATG8 isoforms using both in vivo protein interaction assays and in vitro quantitative binding affinity analyses. These experiments revealed that the N-terminal β-strand -and, in particular, a single amino acid polymorphism- underpins binding specificity to the substrate PexRD54 by shaping the hydrophobic pocket that accommodates this protein′s ATG8 interacting motif. Additional proteomics experiments indicated that the N-terminal...Continue Reading

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Mentioned in this Paper

Gene Polymorphism
In Vivo
Biochemical Pathway
Autophagy-Related Protein 8 Family
Tissue Membrane
Membrane
Regulation of Biological Process
Ubiquitin
MAP1LC3A wt Allele
Ubiquitin Activity

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