Heterogeneity of the cold-insoluble globulin of human plasma (Clg), A circulating cell surface protein

Interactions among Heparin, Cold-Insoluble Globulin, and Fibrinogen in Formation of the Heparin-Precipitable Fraction of Plasma

“…Electrophoresis was carried out for 16 h at 60 V. The rabbit anti-human CIg serum was that previously reported (7). Studies confirming the specificity of this antiserum for CIg have previously been reported (7,19,22,23). The rabbit anti-human fibrinogen serum had been prepared in this laboratory and was specific for fibrinogen (7).…”

“…In contrast, the afibrinogenemic heparin precipitate lacked the major fibrinogen band. In both samples, material with a slower migration rate than the CIg band of mol wt 450,000 probably represented noncovalent aggregates of CIg (23). Reduced samples of the heparin precipitate from normal plasma showed the characteristic band pattern of fibrinogen (i.e., bands corresponding to the Aa, B,3, and y chains, respectively) and a major high molecular weight band corresponding to the position occupied by reduced CIg subunits (not shown).…”

“…8), densitometric analyses were not attempted on such specimens. However, the relative proportion of CIg and fibrinogen in the precipitate from such plasma was assessed by densitometric scanlower molecular weight components bearing CIg antigenic determinants have also been described (23).…”

Identification and isolation of a collagen-binding fragment of the adhesive glycoprotein fibronectin.

“…Chicken cellular fibronectin isolated from cultured embryonic fibroblasts was permitted to bind to gelatin coupled to agarose beads and was then digested extensively with chymotrypsin, A prominent 40,000-dalton fragment of fibronectin consisting of a single polypeptide chain was detected by sodium dodecyl sulfate/polyacrylamide gel electrophoresis of material remaining bound to the gelatin-agarose. This fragment appeared within 10 min after the digestion was initiated and persisted for more than 20 hr. This proteolytic fragment was isolated in electrophoretically pure form and retained its affinity for collagen.…”

“…Partial proteolysis experiments have revealed that there are interchain disulfide bridges only at one end of the fibronectin molecule (11,17,18,20,21). Proteolysis studies can also be used to define regions within protein molecules that have intrinsic tertiary structures resistant to proteolytic digestion.…”