Immunoglobulin homology unit

Wen D, Peles E, Cupples R, Suggs SV, Bacus SS, et al. 1992. Neu differentiation factor A transmembrane glycoprotein containing an EGF domain and an immunoglobulin homology unit. Cell 69 559-572. 

The qualifying feature of the immunoglobulin homology unit is its molecular architecture. Delineation of this structure has resulted from a considerable amount... 

Homology to immunoglobulin units is often weak whilst /3-strand patterns are suggestive of V units, only Thy-1. the membrane-distal unit of MRC OX-2 and the poly-immunoglobulin receptor units possess the extra hairpin loop (C /C") which is characteristic of V units (Fig. 11). Thus, the polypeptide chain may fold in a similar way to C units. Although all these molecules are believed to exist as monomers, in most cases the possibility of homodimeric associations has not been ex-... 

Homology to immunoglobulin units is also found in molecules which are not directly involved in immune recognition. Whilst some of these molecules have no known function (Thy-1, MRC OX-2, a, B-glycoprotein), others clearly interact with homologous molecules either within the immune system (immunoglobulin receptors) or in different systems (NCAM and MAG/Ncp 3). 

A study of the three-dimensional structure of the pF fragment of guinea pig IgGl, a non-covalent dimer of the 0 3 homology sub-unit, is reported.From quantitative H n.m.r. studies on the and pF fragments of rabbit immunoglobulin G it is concluded that there is a two-fold axis of symmetry in these fragments that leads to reduced tine widths. ... 

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