Structural symmetry in homooligomeric proteins has intrigued many researchers over the past several decades. However,\r\nthe implication of protein symmetry is still not well understood. In this study, we performed molecular dynamics (MD)\r\nsimulations of two forms of trp RNA binding attenuation protein (TRAP), the wild-type 11-mer and an engineered 12-mer,\r\nhaving two different levels of circular symmetry. The results of the simulations showed that the inter-subunit fluctuations in\r\nthe 11-mer TRAP were significantly smaller than the fluctuations in the 12-mer TRAP while the internal fluctuations were\r\nlarger in the 11-mer than in the 12-mer. These differences in thermal fluctuations were interpreted by normal mode analysis\r\nand group theory. For the 12-mer TRAP, the wave nodes of the normal modes existed at the flexible interface between the\r\nsubunits, while the 11-mer TRAP had its nodes within the subunits. The principal components derived from the MD\r\nsimulations showed similar mode structures. These results demonstrated that the structural symmetry was an important\r\ndeterminant of protein dynamics in circularly symmetric homooligomeric proteins.
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