Disulphide Bridges of Immunoglobin G1 Heavy Chains

Abstract

THE immunoglobulins G1 represent the major component of human immunoglobulins, with a basic four chain structure consisting of two heavy and two light chains joined by disulphide bridges¹. (The nomenclature used is based on that recommended by the World Health Organization (1966).) The light chains are made up of two sections—an invariable C-terminal section characteristic of each type, and a variable N-terminal section specific to each clone^2–4. Peptide maps of Fd fragments^5,6 suggest that a similar situation holds in heavy chains. In light chains the two sections are folded, each by a single disulphide bridge, to give two loops of almost equal size—the invariable C-terminal loop and the variable N-terminal loop⁷. The Fc region of human G immunoglobulins includes two intrachain disulphide bridges which impose on it a ring structure, again made up of an N-terminal and a C-terminal loop, resembling the ring structure of light chains⁸. In this communication, we present evidence which suggests further similarities between disulphide bridges of light and heavy chains. We also present results concerning a peptide containing both the heavy-light and heavy-heavy interchain disulphide bridges.