Molecular determinants of Xolloid action in vivo.
Xld (Xolloid) is a member of the Tolloid family of metalloproteases found in embryos of the frog Xenopus laevis. It cleaves Chordin, an inhibitory binding protein for BMP2/4, releasing fragments with reduced affinity for these important ventralizing signals. As a consequence, increasing Xld activity ventralizes Xenopus embryos. We have used this phenotype as an assay to determine the requirement for the C-terminal, nonprotease component of Xld for in vivo activity. This part of the protein is composed of five complement C1r/C1s-sea urchin epidermal growth factor-BMP1 (CUB) and two epidermal growth factor domains, which are thought to be involved in protein-protein interactions and may confer substrate specificity. Our results show that the protease coupled to CUB1 and CUB2 is the minimum domain structure required to ventralize Xenopus embryos and to block the dorsal axis-inducing activity of Chordin. Xld-CUB1-CUB2 cleaves Chordin, and a protease-inactive version co-precipitates Chordin. Our results indicate that the first and second CUB domains bind Chordin and present it to the protease domain. Protease-inactive Xld blocks the cleavage of Chordin by wild-type Xld and dorsalizes injected Xenopus embryos. We find that protease-inactive Xld-CUB1-CUB2 does not share this activity and that all of the C-terminal domains are required to generate the dorsalized phenotype.
Geach
Timothy J
TJ
Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom.
Dale
Leslie
L
D000818:Animals; D019521:Body Patterning / Q000502:physiology*; D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
C504610:Bmp2 protein, Xenopus; D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D029867:Xenopus Proteins; C525812:bmp4 protein, Xenopus; C054234:chordin; D008666:Metalloendopeptidases; C109187:TLL2 protein, Xenopus