title: Asymmetry adjacent to the collagen-like domain in rat liver mannose-binding protein.
abstract: Rat liver mannose-binding protein (MBP-C) is the smallest known member of the collectin family of animal lectins, many of which are involved in defence against microbial pathogens. It consists of an N-terminal collagen-like domain linked to C-terminal carbohydrate-recognition domains. MBP-C, overproduced in Chinese-hamster ovary cells, is post-translationally modified and processed in a manner similar to the native lectin. Analytical ultracentrifugation experiments indicate that MBP-C is trimeric, with a weight-averaged molecular mass of approx. 77 kDa. The rate of sedimentation of MBP-C and its mobility on gel filtration suggest a highly elongated molecule. Anomalous behaviour on gel filtration due to this extended conformation may explain previous suggestions that MBP-C forms a higher oligomer. The polypeptide chains of the MBP-C trimer are linked by disulphide bonds between two cysteine residues at the N-terminal junction of the collagen-like domain. Analysis of an N-terminal tryptic fragment reveals that the disulphide bonding in MBP-C is heterogeneous and asymmetrical. These results indicate that assembly of MBP-C oligomers probably proceeds in a C- to N-terminal direction: trimerization at the C-terminus is followed by assembly of the collagenous domain and finally formation of N-terminal disulphide bonds. The relatively simple organization of MBP-C provides a template for understanding larger, more complex collectins.
authors.affiliation: Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
authors.forename: R
authors.initials: R
authors.lastname: Wallis
authors.forename: K
authors.initials: K
authors.lastname: Drickamer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D003094:Collagen / Q000737:chemistry*; D037222:Collectins; D006224:Cricetinae; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D006020:Glycopeptides / Q000032:analysis / Q000737:chemistry; D008099:Liver / Q000737:chemistry*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational / Q000502:physiology; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014461:Ultracentrifugation
chemical_list: D002352:Carrier Proteins; D037222:Collectins; D004220:Disulfides; D006020:Glycopeptides; D010446:Peptide Fragments; D011994:Recombinant Proteins; D003094:Collagen