Monoclonal antibody 1B2-8-2 reacts with Punctin-1 (ADAMTSL-1). Punctin-1 is a secreted molecule resembling members of the family of proteases designated ADAMTS (a disintegrin-like and metalloprotease domain with thrombospondin type I motif). ADAMTS proteases are secreted enzymes that consist of a metalloprotease domain (which provides the catalytic activity) and ancillary domains (which provide substrate, cell or extracellular matrix activity). Punctin-1 lacks the pro-metalloprotease and the disintegrin-like domain typical of this family but contains other ADAMTS domains in precise order including 4 thrombospondin-I repeats. Punctin-1 is an extracellular matrix protein in tissues and deposited into the cell substratum and localized towards the periphery of transfected cells. Punctin-1 and Punctin-2 (ADAMTSL-3) are the first members of a novel family of ADAMTS-like proteins that appear to have important functions in the extracellular matrix. Monoclonal antibody 1B2-8-2 recognizes the first thrombospondin repeat near the N-terminal and reacts with molecular species of 55 kDa or a doublet of 55 k Da and 60 kDa (glycosylated form). Note that proteolysis of Punctin-1 has been described and additional smaller bands may also be obtained.