ABSTRACT
It was the proverbial dark and stormy night (typical of Seattle winters) when we first saw it-an Mr 43,000 band on an SDS-polyacrylamide gel, apparently the major biosynthetic product secreted by cultured endothelial cells. Although heavily labeled with [3H]-proline, the next experiment showed that this protein was not a collagen, a forsaken identity relegating it to the backburner in a laboratory focused primarily (but not entirely) on collagens. My postdoctoral mentor, Paul Bornstein, showed great intellectual generosity (and undoubtedly patience), by allowing me to work on what we termed “43k” (with a promise not to bother him with details “until the manuscript was written”). By all counts this decision was both wise and prophetic, as 43k (now known as SPARC) has provided us with puzzles, insights, and enjoyment over the last 30 years. And, as the story began to unfold, it became clear to us that we were working on far more than the biochemical characterization of a small, extracellular glycoprotein.
