Structure of a peptide : N-glycanase-Rad23 complex: Insight into the deglycosylation for denatured glycoproteins

목차

deep cleft
PNGase
zinc-metalloenzyme

본문내용

In eukaryotes, misfolded proteins must be distinguished from
correctly folded proteins during folding and transport processes by
quality control systems. Yeast peptide:N-glycanase (yPNGase) specifically
deglycosylates the denatured form of N-linked glycoproteins
in the cytoplasm and assists proteasome-mediated glycoprotein
degradation by forming a complex with 26S proteasome
through DNA repair protein, yRad23. Here, we describe the crystal
structures of a yPNGase and XPC-binding domain of yRad23
(yRad23XBD, residues 238–309) complex and of a yPNGase–
yRad23XBD complex bound to a caspase inhibitor, Z-VAD-fmk.
yPNGase is formed with three domains, a core domain containing
a Cys–His–Asp triad, a Zn-binding domain, and a Rad23-binding
domain. Both N- and C-terminal helices of yPNGase interact with
yRad23 through extensive hydrophobic interactions. The active
site of yPNGase is located in a deep cleft that is formed with
residues conserved in all PNGase members, and three sugar molecules
are bound to this cleft. Complex structures in conjunction
with mutational analyses revealed that the walls of the cleft block
access to the active site of yPNGase by native glycoprotein,
whereas the cleft is sufficiently wide to accommodate denatured
glycoprotein, thus explaining the specificity of PNGase for denatured
substrates.

키워드

deep cleft ,   zinc-metalloenzyme,   PNGase,   structure,   protein,   crystal