Gf. Mcintyre et Ah. Erickson, THE LYSOSOMAL PROENZYME RECEPTOR THAT BINDS PROCATHEPSIN-L TO MICROSOMAL-MEMBRANES AT PH 5 IS A 43-KDA INTEGRAL MEMBRANE-PROTEIN, Proceedings of the National Academy of Sciences of the United Statesof America, 90(22), 1993, pp. 10588-10592
Two lysosomal proenzymes, procathepsins L and D, bind to mouse fibrobl
ast microsomal membranes at acidic pH. This membrane association is in
dependent of the mannose-6-phosphate receptors and requires the presen
ce of the N-terminal propeptides of the enzymes. We have identified th
e protein that specifically binds procathepsin L at pH 5. A 43-kDa mem
brane protein coimmunoprecipitated with procathepsin L at pH 5 but not
at pH 7 when cells were denatured with detergents. Similarly, a 43-kD
a integral membrane protein bound procathepsin L in three kinds of lig
and blots at pH 5 but not at pH 7. A synthetic peptide containing the
24 N-terminal residues of mouse procathepsin L blocked the binding of
procathepsin L to this integral membrane protein on ligand blots. Thes
e results indicate that the 43-kDa integral membrane protein is a lyso
somal proenzyme receptor that specifically binds the procathepsin L ac
tivation peptide at acidic pH.