title: Structures of designed armadillo-repeat proteins show propagation of inter-repeat interface effects.
abstract: The armadillo repeat serves as a scaffold for the development of modular peptide-recognition modules. In order to develop such a system, three crystal structures of designed armadillo-repeat proteins with third-generation N-caps (YIII-type), four or five internal repeats (M-type) and second-generation C-caps (AII-type) were determined at 1.8 Å (His-YIIIM4AII), 2.0 Å (His-YIIIM5AII) and 1.95 Å (YIIIM5AII) resolution and compared with those of variants with third-generation C-caps. All constructs are full consensus designs in which the internal repeats have exactly the same sequence, and hence identical conformations of the internal repeats are expected. The N-cap and internal repeats M1 to M3 are indeed extremely similar, but the comparison reveals structural differences in internal repeats M4 and M5 and the C-cap. These differences are caused by long-range effects of the C-cap, contacting molecules in the crystal, and the intrinsic design of the repeat. Unfortunately, the rigid-body movement of the C-terminal part impairs the regular arrangement of internal repeats that forms the putative peptide-binding site. The second-generation C-cap improves the packing of buried residues and thereby the stability of the protein. These considerations are useful for future improvements of an armadillo-repeat-based peptide-recognition system.
authors.affiliation: Department of Biochemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Reichen
authors.affiliation: Department of Biochemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
authors.forename: Chaithanya
authors.initials: C
authors.lastname: Madhurantakam
authors.affiliation: Department of Biochemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
authors.forename: Simon
authors.initials: S
authors.lastname: Hansen
authors.affiliation: Department of Biochemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
authors.forename: Markus G
authors.initials: MG
authors.lastname: Grütter
authors.affiliation: Department of Biochemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Plückthun
authors.affiliation: Department of Biochemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
authors.forename: Peer R E
authors.initials: PR
authors.lastname: Mittl
mesh_terms: D000595:Amino Acid Sequence; D051186:Armadillo Domain Proteins / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D011487:Protein Conformation; D015202:Protein Engineering
chemical_list: D051186:Armadillo Domain Proteins
keywords: armadillo repeat; calcium binding; peptide binding; protein engineering; solenoid protein