Sequence and RFLP analyses of CD151 and structure of CD151 large extracellular region. (A) Sequence and RFLP analyses of CD151. (i) DNA sequence of the MER2^– patient with a hereditary nephritis (Pt2) exhibiting a G383 insertion in CD151 exon 5. The G383 insert introduced a novel recognition site 381GG-ACN₁₀ for BsmF. PCR-RFLP gel analysis: wild-type allele was cut into restriction fragments of 86 and 401 bp and the mutation in 3 MER2-negative patients with end-stage renal disease (Pt1, Pt2, Pt3) caused further reduction of the 401-bp fragment to 2 additional 135- and 266-bp fragments. Lanes are identified as a standard 10-kb DNA ladder (m), blank control (w), uncut allele (u), and control samples (c). (ii) DNA sequence of the MER2^– healthy blood donor D1 with the G533A mutation in CD151 exon 6. The PCR product from D1 was cut at a novel restriction site 528TGG CCA for McsI to fragments of 160 and 326 bp, whereas the wild-type allele was left intact. PCR-RFLP gel analysis lanes labeled as in (i). (iii) Schematic representation of CD151 gene and the relative placement of the 2 mutations. (B) Structure of CD151 large extracellular region. (i, left) Homology model of a monomer of the CD151 large extracellular loop (EC2) is shown as a Cα-ribbon cartoon. The amino terminus (residue 112) is labeled N, and the carboxy terminus (residue 220) is labeled C. Because of the incorporation of a stop codon at position 140 in the MER2^– patients, all residues represented by the green ribbon are not expressed. The side chain is shown for Arg 178 (purple), which is mutated to His in D1. Residues constituting the QRD proposed integrin binding site are shown in red, and the single N-linked glycosylation site (Asn 160) in blue. (ii, right) Tetraspanins readily form homodimers.³¹  Proposed homodimeric assembly of CD151, based on the observed oligomerization in the crystal structure of CD81. Coloring and labels as described for panel i.