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SummaryThe abnormal fibrinogen Haifa is characterized by the fact that calcium present during enzymatic digestion by plasmin does not protect the Haifa D gamma chain against further plasmin attack as it does in normal molecules.Since calcium binding to fibrinogen, ADP - platelet aggregation cofactor activity and gamma dimerization process induced by factor XIIIa are normal for fibrinogen Haifa, the corresponding sequences in the gamma chain are not involved. It seems rather that the anomaly resides near the gamma 302 plasmin cleavage site that is protected when calcium is bound to the gamma chain and that this affects the availability of the polymerization site located in the C terminal part of the chain.

Two-dimensional electrophoresis (2-DE) of cerebrospinal fluid (CSF) samples--from 347 patients with various psychiatric and neurological disorders--and subsequent silver staining revealed two additional polypeptides (Mr 40,000) in 49% of 111 schizophrenics, 46% of 43 schizoaffective patients, 36% of 41 patients with affective disorders, 43% of 28 patients with multiple sclerosis, but not in 25 patients without neurological symptomatology, nor in 9 patients with Lues, and in only 2 of 25 patients with AIDS. The two polypeptides, as detected by 2-DE, eluted after size exclusion chromatography in fractions containing proteins with Mr greater than 200,000. After 2-DE of CSF samples, enriched by gel chromatography, the polypeptides were immobilized by blotting onto glass-fiber membranes and subjected to N-terminal sequencing. Polypeptide A was identified as beta-chain remnant (beta 2), derived from plasmin cleavage of fibrin(ogen). After size exclusion chromatography, 2-DE, and Western blotting, polypeptide A and B, as well as several other spots, reacted with fibrinogen antibodies, suggesting that the polypeptides are subunits of a fibrin degradation complex.

Assessed by high performance liquid chromatographic and amino acid sequence determinations, approximately one half (n = 4) of A peptide in fibrinogen Stony Brook (4 SB) contained the Aal6Arg --Cys substitution. To examine its functional behavior, mutant molecule-rich soluble subfractions that partly or fully lacked their normal A peptide were obtained from cryoprecipitates or from incoagulable material, respectively. Such subfractions consistently induced a more pronounced decrease (n = 3) in the turbidity of normal polymerizing fibrin than that induced by normal fibrinogen, by whole 4 SB (a = 4) or by fibrinogen from an unrelated homozygous proband. These subfractions also exhibited decreased (12-50% of normal controls, fibrinogen 30-590 nM, n = 5) ADP-induced aggregation support of gel-sieved platelets, a decrease not demonstrable by whole 4 SB, by fibrinogen from the homozygous proband, or by enrichment of the latter with normal soluble fibrin. A single isolate displaying diminished platelet aggregation support was 125I-labeled and examined further. It exhibited decreased binding to platelets, and Scatchard analysis indicated decreased binding affinity but normal maximum binding. We infer that 4 SB contained heterodimers that exhibited these distinct functional properties when their normal A peptide had been cleaved.