2RFM

Structure of a Thermophilic Ankyrin Repeat Protein

Summary for 2RFM

• Entry DOI: 10.2210/pdb2rfm/pdb
• Descriptor: Putative ankyrin repeat protein TV1425, SULFATE ION, TRIS-HYDROXYMETHYL-METHYL-AMMONIUM, ... (7 entities in total)
• Functional Keywords: ankyrin repeat, ank repeat, protein binding
• Biological source: Thermoplasma volcanium
• Total number of polymer chains: 2
• Total formula weight: 45155.41

Authors

Loew, C.,Weininger, U.,Neumann, P.,Stubbs, M.T.,Balbach, J. (deposition date: 2007-10-01, release date: 2008-03-11, Last modification date: 2024-03-13)

Primary citation

Loew, C.,Weininger, U.,Neumann, P.,Klepsch, M.,Lilie, H.,Stubbs, M.T.,Balbach, J.
Structural insights into an equilibrium folding intermediate of an archaeal ankyrin repeat protein
Proc.Natl.Acad.Sci.Usa, 105:3779-3784, 2008

PubMed Abstract: Repeat proteins are widespread in nature, with many of them functioning as binding molecules in protein-protein recognition. Their simple structural architecture is used in biotechnology for generating proteins with high affinities to target proteins. Recent folding studies of ankyrin repeat (AR) proteins revealed a new mechanism of protein folding. The formation of an intermediate state is rate limiting in the folding reaction, suggesting a scaffold function of this transient state for intrinsically less stable ARs. To investigate a possible common mechanism of AR folding, we studied the structure and folding of a new thermophilic AR protein (tANK) identified in the archaeon Thermoplasma volcanium. The x-ray structure of the evolutionary much older tANK revealed high homology to the human CDK inhibitor p19(INK4d), whose sequence was used for homology search. As for p19(INK4d), equilibrium and kinetic folding analyses classify tANK to the family of sequential three-state folding proteins, with an unusual fast equilibrium between native and intermediate state. Under equilibrium conditions, the intermediate can be populated to >90%, allowing characterization on a residue-by-residue level using NMR spectroscopy. These data clearly show that the three C-terminal ARs are natively folded in the intermediate state, whereas native cross-peaks for the rest of the molecule are missing. Therefore, the formation of a stable folding unit consisting of three ARs is the necessary rate-limiting step before AR 1 and 2 can assemble to form the native state.

PubMed: 18305166
DOI: 10.1073/pnas.0710657105

Experimental method

X-RAY DIFFRACTION (1.65 Å)