Role of dimerization and substrate exclusion in the regulation of bone morphogenetic protein-1 and mammalian tolloid.
The bone morphogenetic protein (BMP)-1/tolloid metalloproteinases are evolutionarily conserved enzymes that are fundamental to dorsal-ventral patterning and tissue morphogenesis. The lack of knowledge regarding how these proteinases recognize and cleave their substrates represents a major hurdle to understanding tissue assembly and embryonic patterning. Although BMP-1 and mammalian tolloid (mTLD) are splice variants, it is puzzling why BMP-1, which lacks 3 of the 7 noncatalytic domains present in all other family members, is the most effective proteinase. Using a combination of single-particle electron microscopy, small-angle X-ray scattering, and other biophysical measurements in solution, we show that mTLD, but not BMP-1, forms a calcium-ion-dependent dimer under physiological conditions. Using a domain deletion approach, we provide evidence that EGF2, which is absent in BMP-1, is critical to the formation of the dimer. Based on a combination of structural and functional data, we propose that mTLD activity is regulated by a substrate exclusion mechanism. These results provide a mechanistic insight into how alternative splicing of the Bmp1 gene produces 2 proteinases with differing biological activities and have broad implications for regulation of BMP-1/mTLD and related proteinases during BMP signaling and tissue assembly.
Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom.
Richard
R
Berry
Thomas A
TA
Jowitt
Johanna
J
Ferrand
Manfred
M
Roessle
J Günter
JG
Grossmann
Elizabeth G
EG
Canty-Laird
Richard A
RA
Kammerer
Karl E
KE
Kadler
Clair
C
Baldock
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003198:Computer Simulation; D006801:Humans; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D040681:Structural Homology, Protein; D013379:Substrate Specificity; D055394:Tolloid-Like Metalloproteinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
D055394:Tolloid-Like Metalloproteinases; D002118:Calcium