NMR shows hydrophobic interactions replace glycine packing in the triple helix at a natural break in the (Gly-X-Y)n repeat.
Little is known about the structural consequences of the more than 20 breaks in the (Gly-X-Y)(n) repeating sequence found in the long triple helix domain of basement membrane type IV collagen. NMR triple resonance studies of doubly labeled residues within a set of collagen model peptides provide distance and dihedral angle restraints that allow determination of model structures of both a standard triple helix and of a triple helix with a break in solution. Although the standard triple helix cannot continue when Gly is not every third residue, the NMR data support rod-like molecules that have standard triple-helical structures on both sides of a well defined and highly localized perturbation. The GAAVM break region may be described as a "pseudo triple helix," because it preserves the standard one-residue stagger of the triple helix but introduces hydrophobic interactions at the position normally occupied by the much smaller and hydrogen-bonded Gly residue of the repeating (Gly-X-Y)(n) sequence. This structure provides a rationale for the consensus presence of hydrophobic residues in breaks of similar length and defines a novel variant of a triple helix that could be involved in recognition.
Li
Yingjie
Y
Department of Chemistry and Chemical Biology, BIOMAPS Institute, Rutgers, the State University of New Jersey, Piscataway, New Jersey 08854, USA.
Brodsky
Barbara
B
Baum
Jean
J
D000595:Amino Acid Sequence; D024141:Collagen Type IV / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013816:Thermodynamics
D024141:Collagen Type IV; D010455:Peptides; D005998:Glycine