Protein complex located on the matrix side of the mitochondrial inner membrane and associated with the TIM23 mitochondrial import inner membrane translocase complex (GO:0005744); ATPase motor activity to drive import of proteins into the mitochondrial matrix. [ http://www.ncbi.nlm.nih.gov/pubmed/14517234 http://www.ncbi.nlm.nih.gov/pubmed/14638855 ]