Endocrinology, Vol 123, 2662-2667, Copyright © 1988 by Endocrine Society

ARTICLES

Biological, immunological, and binding properties of recombinant mouse placental lactogen-I

P Colosi, L Ogren, JN Southard, G Thordarson, DI Linzer and F Talamantes
Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208.

Mouse placental lactogen-I (mPL-I) cDNA was inserted into a eukaryotic expression vector and introduced into Chinese hamster ovary cells. Cell lines that secrete high concentrations of mPL-I were isolated, and this glycoprotein was purified from the cell culture-conditioned medium. Recombinant mPL-I (mPL-Ir) is very similar to placental mPL-I (mPL-Ip) in its recognition by polyclonal antisera raised against either mPL-Ip or mPL-Ir, in displacing [125I]iodo-mPL-II from binding sites on mouse liver microsomal membranes, and in stimulating the synthesis of alpha- lactalbumin in primary cultures of mouse mammary epithelial cells. Structural comparison of mPL-Ir and mPL-Ip by sodium dodecyl sulfate- polyacrylamide gel electrophoresis indicated that mPL-Ir comprises several proteins with mol wt ranging from 34.5-38K, while mPL-Ip consists of a similar set of proteins with mol wt ranging from 36.5- 42K. Treatment of the two proteins with neuraminidase resulted in similar 2-4K decreases in mol wt. Treatment of mPL-Ip with peptide:N- glycosidase-F to remove asparagine-linked oligosaccharide chains resulted in the formation of 28K and 29K mol wt species, while treatment of mPL-Ir with the same enzyme yielded 28K and 28.5K mol wt products.

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