Bone
Morphogenetic Proteins (BMP) are members of the TGF beta
superfamily of cytokines that affect bone and cartilage
formation. Similar to other TGF beta family proteins, BMPs
are highly conserved across animal species. Mature BMPs
are 30-38 kDa proteins that assume a TGF beta like cysteine
knot configuration. Unlike TGF beta, BMPs do not form latent
complexes with their propeptide counterparts. Most BMPs
are homodimers, but bioactive natural heterodimers have
been reported. BMPs create an environment conducive for
bone marrow development by stimulating the production of
specific bone matrix proteins and altering stromal cell
and osteoclast proliferation. In addition to stimulating
ectopic bone and cartilage development, BMPs may be an
important factor in the development of the viscera, with
roles in cell proliferation, apoptosis, differentiation,
and morphogenesis. BMPs also appear to be responsible for
normal dorsal/ventral patterning. BMPs are found in tissues
that induce bone or cartilage growth, such as demineralized
bone and urinary epithelium. Cellular responses to BMP5
are mediated by the formation of hetero-oligomeric complexes
of type I and type II serine/threonine kinase receptors
which play significant roles in BMP binding and signaling.
One BMP type II receptor and two BMP type I receptors have
been identified.
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