Structure of puromycin-sensitive aminopeptidase and polyglutamine binding

Abstract

Puromycin-sensitive aminopeptidase (E.C. 3.4.11.14, UniProt P55786), a zinc 6 metallopeptidase belonging to the M1 family, degrades a number of bioactive peptides as 7 well as peptides released from the proteasome, including polyglutamine. We report the 8 crystal structure of PSA at 2.3 Ǻ. Overall, the enzyme adopts a V-shaped architecture 9 with four domains characteristic of the M1 family aminopeptidases, but it is in a less 10 compact conformation compared to most M1 enzymes of known structure. A microtubule 11 binding sequence is present in a C-terminal HEAT repeat domain of the enzyme in a position where it might serve to mediate interaction with tubulin. 12 In the catalytic 13 metallopeptidase domain, an elongated active site groove lined with aromatic and 14 hydrophobic residues and a large S1 subsite may play a role in broad substrate 15 recognition. The structure with bound polyglutamine shows a possible interacting mode 16 of this peptide, which is supported by mutation.