The Binding and Cleavage Characteristics of Human Hageman Factor during Contact Activation

Abstract

A B S T R A C T The ability of human Hageman factor (coagulation factor XII) to bind to a glass surface and its susceptibility to limited proteolytic cleavage during the contact activation of plasma have been studied using normal human plasma and plasmas genetically deficient in factor XI, prekallikrein, or high molecular weight kininogen (HMWK). When diluted normal plasma containing 125I-Hageman factor was exposed to a glass surface for varying times, the Hageman factor was found to bind to the surface, and within 5 min became maximally cleaved from its native 80,000 mol wt to yield fragments of 52,000 and 28,000 mol wt. Hageman factor in factor XI-deficient plasma behaved similarly. In prekallikrein-deficient plasma, the binding of Hageman factor to the glass surface occurred at the same rate as in normal plasma but the cleavage was significantly slower, and did not reach maximum until 60 min of incubation. Cleavage of Hageman factor in HMWK-deficient plasma occurred at an even slower rate, with greater than 110 min of incubation required for maximal cleavage, although the rate of binding to the glass was again the same as in normal plasma. Normal rates of cleavage of Hageman factor were observed for the deficient plasmas after reconstitution with purified human prekallikrein or HMWK, respectively. These observations suggest that normal contact activation in plasma is associated with proteolytic activation of surfacebound Hageman factor.Portions of this work have appeared in abstract form (1976. Fed. Proc. 35: 692).Dr.

Role of surface in surface-dependent activation of Hageman factor (blood coagulation Factor XII)

“…The limited proteolytic cleavage of human HF by different proteases was studied by following the cleavage of the 125I-HF zymogen at 80,000 Mr to give fragments near 5g,000 and 28,000 Mr as assessed using NaDodSO4 gel analysis (20,21,32). The cleavage of 125I-HF by kallikrein was linear with time during the cleavage of greater than 50% of the HF molecules (32).…”

“…In studies similar to those described above (Figs. 1-3 (20). These polypeptides represent The value for kallikrein in the cleavage of surface-bound HF is that observed in the presence of high-Mr kininogen.…”

“…the two major forms of activated HF, a single chain 28,000-Mr molecule and a disulfide-linked two-chain 80,00Mr molecule containing a heavy chain of 52,000 Mr in addition to the 28,000-Mr polypeptide (20). These observations on the rapid cleavage of 125I-HF in plasma and the results reported here support the hypothesis that surface binding of HF causes a conformational change in the molecule which results in a structure that is much more susceptible to proteolytic activation (32).…”

“…The The cleavage of 125I-HF in each reaction mixture was assessed using NaDodSO4 gel analysis in the presence of 2-mercaptoethanol (20,21,32). On reduced NaDodSO4 gels, the 125I-HF gave only three peaks, which corresponded to apparent molecular weights of 80,000, 52,000, and 28,000.…”

“…These data, together with the observations that surface-bound HF is rapidly cleaved in plasma during contact activation in glass tubes (20) and that HF in solution can be proteolytically activated by plasmin, kallikrein, Factor XIa, or trypsin (21)(22)(23)(24), stimulated the present quantitative studies of the cleavage of purified human HF by these proteases in the presence and absence of various surface materials and high-Mr kininogen. In this report the limited proteolysis of l25I-labeled HF (125I-HF) was assessed using sodium dodecyl sulfate (NaDodSO4) gel analysis to follow the cleavage of the 80,000 Mr single chain HF zymogen to give fragments of approximately 52,000 and 28,000 Mr.…”