Showing papers by "Bart De Strooper published in 1992"

The primary sequence and the subunit structure of mouse alpha-2-macroglobulin, deduced from protein sequencing of the isolated subunits and from molecular cloning of the cDNA.

Abstract: Mouse plasma cr-2-macroglobulin (ma2M) was isolated and the N-terminal amino-acid sequences determined after separation of the 165-kDa and 35-kDa subunits. These sequences were compared to the protein sequence predicted by the cDNA, which was cloned from a mouse liver library and sequenced. From these data it is evident that both subunits are encoded by one mRNA of approximately 5 kb expressed predominantly in liver. The smaller subunit, with the N-terminal sequence DLSSSDLT, comprises the C-terminal 257 residues of ma2M and is derived from a single-chain precursor probably by proteolytic processing at an arginine residue in the sequence PTRDLSS. Analysis of the predicted protein further showed all the salient features of a proteinase inhibitor of the macroglobulin family: a bait region that deviates from all known sequences in this family, a very conserved internal thiolester site and conserved cysteine residues and putative N-glycosylation sites. The synthesis of ma2M in adult liver was demonstrated by Northern blotting and in fetal liver by in-situ hybridization. Transient transfection of COS cells with the cDNA under control of a viral promoter demonstrated the secretion and partial processing of ma2M in the culture medium. In plasma the level of ma2M was found to be stable as expected for the murine counterpart of human plasma a-%-macroglobulin. The possibilities of using the mouse as a genetic model to study this proteinase inhibitor in vivo are discussed. Proteinase inhibitors of the a-2-macroglobulin (a2M) family continue to yield information on crucial aspects of the mechanism by which they bind proteinases and eliminate them from the circulation and from the extracellular spaces (for reviews see Van Leuven, 1982; Sottrup- Jensen, 1989; Delain et al., 1992). The widespread occurrence of these inhibitors, in widely different species like arthropods and mammals, their presence in different molecular forms in most species examined, their occurrence in blood, in other body fluids and in other compartments, like in eggs, their specific expression under different physiological conditions like infection (rat acute-phase a2M) or pregnancy (human pregnancy zone protein) are indications for an important role in vivo. This role, however, is far from being known in the same detail as the structure of these proteinase inhibitors. The similarity to complement components C3, C4 and C5 would indicate that these proteinase inhibitors are also essential parts of one or the other protective system. Their Correspondence to F. van Leuven, Center for Human Genetics,