3D Structure: Crystal sturcture of the nitrogen regulation fragment of the Yeast Prion Protein Ure2p
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This tutorial describes residues 97-354 (pictured) of regulatory protein Ure2p, the protein that regulates nitrogen catabolism in yeast.
Reset protein sturcture
This protein has two chains: A
and B
Naturally, the "nitrogen regulation fragment" contains many Nitrogen atoms
The N-terminal "prion domain" of Ure2p (residues 1-80, not shown) is asparagine-rich which aids in efficient generation of URE3 (a yeast nonchromosomal gene). Asparagine is also found in residues 97-354
The yeast two-hybrid system has shown that the C-terminal residues (153-354)
interact with the N-terminal residues (97-151 of 1-151)
The domain interface is formed by alpha helices
in each chain and has hydrophobic and hydrogen bonding interactions with a single salt bridge between Glu 134 and Arg 344
Ure2p contains prion-inhibiting regions
as well as prion-promoting regions
Part of the C-terminal domain contains the "clipped region"
This is one difference between Ure2p and glutathione S-transferase (GST) proteins which have the same folding pattern and much sequence similarity.
The two Ure2p Monomers look identical upon first glance, but the phenyl group of Phe-295 in the B Monomer makes fewer hydrophobic interactions and is more exposed than the corresponding group in Monomer A
One reason Ure2p is thought to be functionally significant is because of its ability to interact through crystal contacts. The residues involved in the crystal contacts are near the proteolytic clip sites of each monomer and interact with the cleft formed between the domains of a symmetry related monomer. Phe 295, Asp 296 and Tyr 297
are inserted into the cleft, while Asp-267 and Tyr-272
interact with the cleft's outer edge.