This can be attributed to the extended side-chain length of hArg/Arg and their delocalized positive charges, which potentially stabilize the Max-DNA complex through the guanidinium and phosphodiester interactions. Additionally, both mutations of Ala17 and Ala21 to Aib resulted in gain-of-function, potentially by contributing to the helicity of the basic domain. On the other hand, we found that mutations at core residues that directly interact with DNA bases generally led to a reduction in activity. Notably, an exception was observed at His19, where mutating it to Tha or Tyr improved the DNA binding activity.