title: Conformational features of a natural break in the type IV collagen Gly-X-Y repeat.
abstract: Fibrillar collagens have an absolute requirement for Gly as every 3rd residue, whereas breaks in the Gly-X-Y repeating pattern are found normally in the triple helix domains of non-fibrillar collagens, such as type IV collagen in basement membranes. In this study, a model 30-mer peptide is designed to include the interruption GPOGAAVMGPOGPO found in the alpha5 chain of type IV collagen. The GAAVM peptide forms a stable triple helix, with Tm= 29 degrees C. When compared with a control peptide with Gly as every 3rd residue, the GAAVM peptide has a marked decrease in the 225 nm maximum of its CD spectrum and a 10 degrees C drop in stability. A 50% decrease in calorimetric enthalpy is observed, which may result from disruption of ordered water structure anchored by regularly placed backbone carbonyls. NMR studies on specific 15N-labeled residues within the GAAVM peptide indicate a normal triple helical structure for Gly-Pro-Hyp residues flanking the break. The sequence within the break is not disordered but shows altered hydrogen exchange rates and an abnormal Val chemical shift. It was previously reported that a peptide designed to model a similar kind of interruption in the peptide (Pro-Hyp-Gly)10, (GPOGPOPOGPO), is unable to form a stable triple helix, and replacement of GAA by GPO or VM by PO within the GAAVM break decreases the stability. Thus, rigid imino acids are unfavorable within a break, despite their favorable stabilization of the triple helix itself. These results suggest some non-random structure typical of this category of breaks in the Gly-X-Y repeat of the triple helix.
authors.affiliation: Department of Biochemistry, University of Medicine and Dentistry of New Jersey (UMDNJ)-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854.
authors.forename: Angela
authors.initials: A
authors.lastname: Mohs
authors.affiliation: Department of Biochemistry, University of Medicine and Dentistry of New Jersey (UMDNJ)-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Popiel
authors.affiliation: Department of Chemistry, Rutgers University, Piscataway, New Jersey 08854.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Chemistry, Rutgers University, Piscataway, New Jersey 08854.
authors.forename: Jean
authors.initials: J
authors.lastname: Baum
authors.affiliation: Department of Biochemistry, University of Medicine and Dentistry of New Jersey (UMDNJ)-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854. Electronic address: brodsky@umdnj.edu.
authors.forename: Barbara
authors.initials: B
authors.lastname: Brodsky
mesh_terms: D000595:Amino Acid Sequence; D002152:Calorimetry, Differential Scanning; D002244:Carbon / Q000737:chemistry; D024141:Collagen Type IV / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013696:Temperature; D013816:Thermodynamics
chemical_list: D024141:Collagen Type IV; D010455:Peptides; D002244:Carbon; D005998:Glycine