The disposition of the LZCC protein residues in wenxiang diagram provides new insights into the protein–protein interaction mechanism

Wenxiang diagram is a new two-dimensional representation that characterizes the disposition of hydrophobic and hydrophilic residues in α-helices. In this research, the hydrophobic and hydrophilic residues of two leucine zipper coiled-coil (LZCC) structural proteins, cGKIα1−59 and MBSCT35 are dispositioned on the wenxiang diagrams according to heptad repeat pattern (abcdefg)n, respectively. Their wenxiang diagrams clearly demonstrate that the residues with same repeat letters are laid on same side of the spiral diagrams, where most hydrophobic residues are positioned at a and d, and most hydrophilic residues are localized on b, c, e, f and g polar position regions. The wenxiang diagrams of a dimetric LZCC can be represented by the combination of two monomeric wenxiang diagrams, and the wenxiang diagrams of the two LZCC (tetramer) complex structures can also be assembled by using two pairs of their wenxiang diagrams. Furthermore, by comparing the wenxiang diagrams of cGKIα1−59 and MBSCT35, the interaction between cGKIα1−59 and MBSCT35 is suggested to be weaker. By analyzing the wenxiang diagram of the cGKIα1−59.·MBSCT42 complex structure, most affected residues of cGKIα1−59 by the interaction with MBSCT42 are proposed at positions d, a, e and g of the LZCC structure. These findings are consistent with our previous NMR results. Incorporating NMR spectroscopy, the wenxiang diagrams of LZCC structures may provide novel insights into the interaction mechanisms between dimeric, trimeric, tetrameric coiled-coil structures.

► cGKIα1−59·MBSCT35 hexamer complex can be represented by a combined wenxiang diagrams.
► These diagrams characterize the interaction between these two LZCC structures.
► The findings by using wenxiang diagram method are consistent with the NMR results.