Molecular analysis of muskelin identifies a conserved discoidin-like domain that contributes to protein self-association.
Muskelin is an intracellular protein with a C-terminal kelch-repeat domain that was initially characterized as having functional involvement in cell spreading on the extracellular matrix glycoprotein thrombospondin-1. As one approach to understanding the functional properties of muskelin, we have combined bioinformatic and biochemical studies. Through analysis of a new dataset of eight animal muskelins, we showed that the N-terminal region of the polypeptide corresponds to a predicted discoidin-like domain. This domain architecture is conserved in fungal muskelins and reveals a structural parallel between the muskelins and certain extracellular fungal galactose oxidases, although the phylogeny of the two groups appears distinct. In view of the fact that a number of kelch-repeat proteins have been shown to self-associate, co-immunoprecipitation, protein pull-down assays and studies of cellular localization were carried out with wild-type, deletion mutant and point mutant muskelins to investigate the roles of the discoidin-like and kelch-repeat domains. We obtained evidence for cis- and trans-interactions between the two domains. These studies provide evidence that muskelin self-associates through a head-to-tail mechanism involving the discoidin-like domain.
Prag
Soren
S
Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Collett
Georgina D M
GD
Adams
Josephine C
JC
D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D030161:Avian Proteins / Q000737:chemistry; D015815:Cell Adhesion Molecules; D002460:Cell Line; D002938:Ciona intestinalis / Q000235:genetics; D017124:Conserved Sequence / Q000502:physiology*; D019281:Dimerization; D000070821:Discoidins; D029721:Drosophila Proteins / Q000737:chemistry; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007668:Kidney / Q000737:chemistry / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D037102:Lectins / Q000737:chemistry*; D051379:Mice; D008969:Molecular Sequence Data; D032448:Myoblasts, Skeletal / Q000737:chemistry; D010455:Peptides / Q000737:chemistry / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000502:physiology; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins / Q000737:chemistry*; D051381:Rats; D020449:Repetitive Sequences, Amino Acid / Q000502:physiology; D016415:Sequence Alignment / Q000379:methods; D014162:Transfection / Q000379:methods; D015027:Zebrafish / Q000235:genetics; D029961:Zebrafish Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D030161:Avian Proteins; D015815:Cell Adhesion Molecules; D000070821:Discoidins; D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D037102:Lectins; C503019:MKLN1 protein, human; C503020:Mkln1 protein, mouse; C503021:Mkln1 protein, rat; D010455:Peptides; D011506:Proteins; D015800:Protozoan Proteins; D029961:Zebrafish Proteins