Defining the repeating elements in the cysteine-rich region (CRR) of the CD18 integrin beta 2 subunit

The cysteine-rich region (CRR) of the integrin beta subunits is organised into four repeating elements. By expression of a panel of truncated beta 2 subunits, and CRR segments fused to the C-terminal end of a CD4 soluble fragment, the segment required for the expression of two monoclonal antibody conformational epitopes was determined. This segment, E482-Q574, contains 16 cysteines representing two repeating units. We have thus defined the CRR unit motif of 'xC---C---C---CxCxxCxC---Cx', where 'x' represents a single residue, and '---' represents a stretch of four to 14 residues.