Role of interchain disulfide bonds on the assembly and secretion of human fibrinogen.

J.Z Zhang,C.M Redman

doi:10.1016/s0021-9258(17)42399-4

Abstract

The cysteines involved in joining the 2 half-molecules of fibrinogen and also those located on either side of the alpha-helical coiled-coil region, were substituted, by site-directed mutagenesis, with serine. Fibrinogen assembly and secretion were determined in transiently transfected COS cells. Our studies indicate that in order to assemble the 2 half-molecules into a dimer, it is not sufficient to only have the disulfide linkages which keep the 2 half-molecules intact. The disulfide rings which flank the coil-coiled region also play important roles in dimer assembly. Intact interchain disulfide linkages at the NH2-terminal end of the coiled-coil region are essential for assembly of the 2 half-molecules. Disruption of these disulfide rings leads to the formation and secretion of half-molecules. Disruption of the interchain disulfide rings at the COOH-terminal end of the coiled-coil region allows dimer formation, but the 6-chain molecule which is assembled is not secreted. Disruption of both disulfide rings at either end of the coiled-coil region disallows assembly of half-molecules and of dimeric fibrinogen.

Highlights

The principal site of fibrinogen synthesis is hepatocytes [17], andsecretionweredeterminedintransientlytransand we have studied the synthesis,assembly, and secretion of fected COS cells
Human fibrinogen is a dimeric molecule composed of 2 half- which accumulated intracellularly in HepG2 and transfected molecules, with each half-molecule containing 3 nonidentical BHK cells expressing fibrinogen were characterized by twopolypeptide chains
The centranl ode (E domain) contains theNH2 termini did not form AwBP complexes, and this 2-chain complex was of the 6 polypeptide chains, and the two terminal nodes (D not found to accumulate inBHK cells or in HepG2 cells incudomains) are formed by globular COOH-terminal domains of bated for 18 h with radioactive amino acid precursor[22]

Summary

Introduction

The principal site of fibrinogen synthesis is hepatocytes [17], andsecretionweredeterminedintransientlytransand we have studied the synthesis,assembly, and secretion of fected COS cells. Disruption of all 3 disulfide bonds which occurs when normal Aa and BP76,80s and y19,23s were co-expressedalso led to the accumulation and secretion of half-molecules.and Aa.y complex, and again very little dimeric fibrinogen was formed (Fig. 4, lane 3).

Results

Conclusion