title: Order within disorder: aggrecan chondroitin sulphate-attachment region provides new structural insights into protein sequences classified as disordered.
abstract: Structural investigation of proteins containing large stretches of sequences without predicted secondary structure is the focus of much increased attention. Here, we have produced an unglycosylated 30 kDa peptide from the chondroitin sulphate (CS)-attachment region of human aggrecan (CS-peptide), which was predicted to be intrinsically disordered and compared its structure with the adjacent aggrecan G3 domain. Biophysical analyses, including analytical ultracentrifugation, light scattering, and circular dichroism showed that the CS-peptide had an elongated and stiffened conformation in contrast to the globular G3 domain. The results suggested that it contained significant secondary structure, which was sensitive to urea, and we propose that the CS-peptide forms an elongated wormlike molecule based on a dynamic range of energetically equivalent secondary structures stabilized by hydrogen bonds. The dimensions of the structure predicted from small-angle X-ray scattering analysis were compatible with EM images of fully glycosylated aggrecan and a partly glycosylated aggrecan CS2-G3 construct. The semiordered structure identified in CS-peptide was not predicted by common structural algorithms and identified a potentially distinct class of semiordered structure within sequences currently identified as disordered. Sequence comparisons suggested some evidence for comparable structures in proteins encoded by other genes (PRG4, MUC5B, and CBP). The function of these semiordered sequences may serve to spatially position attached folded modules and/or to present polypeptides for modification, such as glycosylation, and to provide templates for the multiple pleiotropic interactions proposed for disordered proteins.
authors.affiliation: Wellcome Trust Centre for Cell Matrix Research, University of Manchester, Manchester, M13 9PT, United Kingdom. t.jowitt@manchester.ac.uk
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Jowitt
authors.forename: Alan D
authors.initials: AD
authors.lastname: Murdoch
authors.forename: Clair
authors.initials: C
authors.lastname: Baldock
authors.forename: Richard
authors.initials: R
authors.lastname: Berry
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Day
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Hardingham
mesh_terms: D053674:Aggrecans / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D000595:Amino Acid Sequence; D001665:Binding Sites; D002809:Chondroitin Sulfates / Q000737:chemistry* / Q000378:metabolism*; D019295:Computational Biology; D006801:Humans; D057446:Hydrodynamics; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D011489:Protein Denaturation / Q000187:drug effects; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D053838:Scattering, Small Angle; D040681:Structural Homology, Protein; D014508:Urea / Q000494:pharmacology; D014961:X-Ray Diffraction
chemical_list: D053674:Aggrecans; D010455:Peptides; D014508:Urea; D002809:Chondroitin Sulfates
references.citation: Nat Struct Mol Biol. 2009 Jul;16(7):684-90
references.pmid: 19525973
references.citation: Proc Natl Acad Sci U S A. 1998 May 12;95(10):5480-3
references.pmid: 9576907
references.citation: Science. 1985 Aug 30;229(4716):834-8
references.pmid: 4023714
references.citation: Biochem J. 1992 Oct 1;287 ( Pt 1):183-5
references.pmid: 1417771
references.citation: Biochem J. 1998 Jan 15;329 ( Pt 2):415-24
references.pmid: 9425127
references.citation: J Colloid Sci. 1949 Feb;4(1):35-70
references.pmid: 18110601
references.citation: Proc Natl Acad Sci U S A. 2004 Aug 24;101(34):12497-502
references.pmid: 15314216
references.citation: Biochem J. 1989 Apr 15;259(2):471-6
references.pmid: 2719660
references.citation: Adv Protein Chem. 1968;23:121-282
references.pmid: 4882248
references.citation: Protein Sci. 1994 Dec;3(12):2395-410
references.pmid: 7756993
references.citation: Annu Rev Biophys. 2008;37:215-46
references.pmid: 18573080
references.citation: J Struct Biol. 2003 Sep;143(3):242-57
references.pmid: 14572479
references.citation: Biophys J. 2000 Mar;78(3):1606-19
references.pmid: 10692345
references.citation: J Mol Biol. 1995 Dec 15;254(5):960-7
references.pmid: 7500363
references.citation: J Mol Biol. 1999 Sep 17;292(2):195-202
references.pmid: 10493868
references.citation: Nature. 1979 Feb 8;277(5696):491-2
references.pmid: 763335
references.citation: Nat Rev Mol Cell Biol. 2005 Mar;6(3):197-208
references.pmid: 15738986
references.citation: J Mol Biol. 2007 Sep 28;372(4):970-980
references.pmid: 17686488
references.citation: Biochem J. 1987 Aug 1;245(3):763-72
references.pmid: 3663190
references.citation: J Biol Chem. 1999 Dec 31;274(53):38107-11
references.pmid: 10608880
references.citation: Curr Opin Struct Biol. 2008 Dec;18(6):756-64
references.pmid: 18952168
references.citation: Nucleic Acids Res. 2003 Jul 1;31(13):3381-5
references.pmid: 12824332
references.citation: BMC Genomics. 2008 Sep 16;9 Suppl 2:S1
references.pmid: 18831774
references.citation: Protein Sci. 2002 Apr;11(4):980-5
references.pmid: 11910041
references.citation: Proc Natl Acad Sci U S A. 2002 Jul 9;99(14):9190-5
references.pmid: 12091708
references.citation: Biochemistry. 1978 Oct 3;17(20):4277-85
references.pmid: 708713
references.citation: Biochemistry. 2005 Apr 26;44(16):6269-75
references.pmid: 15835915
references.citation: Structure. 2008 Jan;16(1):93-103
references.pmid: 18184587
references.citation: Proc Natl Acad Sci U S A. 2004 Feb 3;101(5):1279-84
references.pmid: 14734808
references.citation: Bioinformatics. 2002 Nov;18(11):1508-14
references.pmid: 12424123
references.citation: Structure. 2004 Aug;12(8):1495-506
references.pmid: 15296743
references.citation: Structure. 2005 May;13(5):723-34
references.pmid: 15893663
references.citation: Protein Sci. 2006 Jan;15(1):74-83
references.pmid: 16373476
references.citation: Biophys J. 2007 Jan 1;92(1):225-33
references.pmid: 17028145
references.citation: FASEB J. 1992 Feb 1;6(3):861-70
references.pmid: 1740236
references.citation: Biochemistry. 2001 Mar 27;40(12):3427-38
references.pmid: 11297408
references.citation: Protein Sci. 1999 Mar;8(3):587-95
references.pmid: 10091661