Apocytochrome b5 with a typical heme-binding motif of HPGG, and its variants with mutated motifs, GPGG, GPGH, HVGG, and HPGP, have been subjected to molecular dynamics simulation. Comparison of the dynamic consequences has revealed the crucial role of HPGG in assembling the heme group of cytochrome b5 and in modulating protein structure, pro...