Disulfide bridges, transferrins

With the advent of monoclonal antibodies, the search for tumour-specific antigens became the biggest cottage industry since unemployment. It rapidly became apparent that a 90 kD disulfide-bridged transmembrane protein was present in many tumour cells - it was the transferrin receptor, and as they say, the rest is history. It has become a standard procedure to determine the in vivo growth potential of tumours by measuring transferrin receptor expression. 

Fig. 6. Pattern of disulfide bridges commonly found in transferrins. Numbering corresponds to that introduced by Williams (87) and used in Table V. Figure taken from Bailey et al. (68), with permission.

The position of disulfide bridges within the two halves of the peptide chain are highly conserved in transferrins. 

Another variation that may affect the dynamic properties of different transferrins is in the number and distribution of disulfide bonds. Because conformational change is important for metal binding and release (Section V) the restraints imposed by these covalent bridges may be important. The likely distribution of disulfide bonds in different species is given in Table V. While these are deduced from sequence alignments and are thus tentative, several conclusions can be drawn. All species appear to have the same six conserved disulfide bonds in their N-lobe... 

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