Structure of the human desmoplakins: Implications for function in the desmosomal plaque

Desmoplakins (DPs) I and II are two major related proteins located in the innermost portion of the desmosomal plaque where it is thought they may play a role in attaching intermediate filaments (IF) to the cell surface. We have isolated and sequenced human cDNA clones encoding two major DP domains and a portion of a third. These clones can be divided into two classes that we believe to represent DPI and DPII cDNAs; our evidence suggests that the DPII message is derived at least in part from the processing of a larger transcript encoded by a single gene. Computer-aided analysis of the DPI-predicted amino acid sequence indicates that the central domain, which contains the heptad repeat characteristic of many α-fibrous proteins, will participate in the formation of a coiled coil dimer ∼130 nm in length. The periodicity of acidic and basic residues in the rod suggests that DPI will aggregate with itself or similar molecules into higher order filamentous structures. The carboxyl terminus contains three regions with significant homology, each of which comprises almost five repeats of a 38-residue motif. It is likely that these regions each fold into a compact globular conformation stabilized by intrachain ionic interactions. Comparison of the predicted amino acid sequence of a cDNA encoding a portion of the 230-kDa bullous pemphigoid antigen (Stanley, J. R., Tanaka, T., Mueller, S., Klaus-Kovtun, V., and Roop, D. (1988) J. Clin. Invest. 82, 1864-1870) with DP revealed the presence of a 38-residue repeat with striking similarity to that of the DPs. Significantly, the periodicity in acidic and basic residues of these domains is the same as that found in the 1B rod domain of IF proteins. This suggests the possibility that the DPs might interact with IF via their common periodicity of charged residues.