Title : Post-translational modification of
bone morphogenetic protein-1 is required for secretion and stability of the protein
Abstract :
- Bone morphogenetic protein (BMP)-1 is a glycosylated metalloproteinase that is fundamental to the synthesis of a normal extracellular matrix because it cleaves type I procollagen , as well as other precursor proteins
- Sequence analysis suggests that BMP-1 has six potential N-linked glycosylation sites (i.e. NXS/T) namely: Asn(91) ( prodomain ), Asn(142) ( metalloproteinase domain ), Asn(332) and Asn(363) (CUB1 domain ), Asn(599) (CUB3 domain ), and Asn(726) in the C-terminal-specific domain
- In this study we showed that all these sites are N-glycosylated with complex-type oligosaccharides containing sialic acid, except Asn(726) presumably because proline occurs immediately C-terminal of threonine in the consensus sequence
- Recombinant BMP-1 molecules lacking all glycosylation sites or the three CUB-specific sites were not secreted
- BMP-1 lacking CUB glycosylation was translocated to the proteasome for degradation
- BMP-1 molecules lacking individual glycosylation sites were efficiently secreted and exhibited full procollagen C-proteinase activity, but N332Q and N599Q exhibited a slower rate of cleavage
- BMP-1 molecules lacking any one of the CUB-specific glycosylation sites were sensitive to thermal denaturation
- The study showed that the glycosylation sites in the CUB domains of BMP-1 are important for secretion and stability of the molecule