Proteolipid and bone matrix calcification in vitro

Proteolipid was demonstrated to contain the nucleator of bone matrix calcification, in vitro. Crude phospholipid extracted from bone matrix was fractionated by gel filtration. A single, protein-containing fraction induced apatite crystallization in a metastable calcium phosphate solution. The fraction was identified as proteolipid. The result supports the validity of a microbiologic analogue for vertebrate calcification.