The crystal structure of the nitrogen regulation fragment of the yeast prion protein Ure2p

The crystal structure of the nitrogen regulation fragment of the yeast prion protein Ure2p

Laboratories of ^*Molecular Biology and ^†Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0560

Contributed by David R. Davies

Abstract

The yeast nonchromosomal gene [URE3] is due to a prion form of the nitrogen regulatory protein Ure2p. It is a negative regulator of nitrogen catabolism and acts by inhibiting the transcription factor Gln3p. Ure2p residues 1–80 are necessary for prion generation and propagation. The C-terminal fragment retains nitrogen regulatory activity, albeit somewhat less efficiently than the full-length protein, and it also lowers the frequency of prion generation. The crystal structure of this C-terminal fragment, Ure2p(97–354), at 2.3 Å resolution is described here. It adopts the same fold as the glutathione S-transferase superfamily, consistent with their sequence similarity. However, Ure2p(97–354) lacks a properly positioned catalytic residue that is required for S-transferase activity. Residues within this regulatory fragment that have been indicated by mutational studies to influence prion generation have been mapped onto the three-dimensional structure, and possible implications for prion activity are discussed.

Footnotes

↵ ‡ Present address: Nabi, Rockville, MD 20852.
↵ § Present address: School of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seodoon-Dong, Suwon, Korea.
↵ ¶ To whom reprint requests should be addressed. E-mail: drd{at}vger.niddk.nih.gov.
Data deposition: The atomic coordinates have been deposited in the Protein Data Bank, www.rcsb.org (PDB ID code 1HQO).
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.041607898.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.041607898
Abbreviations:

GST,

glutathione S-transferase;

GSH,

reduced glutathione;

ncs,

noncrystallographic symmetry;

G-site,

glutathione-binding site;

H-site,

hydrophobic electrophile-binding site