text: The dynamic components that vary in concentration on kinetochores during mitosis include the molecular motors CENP-E and dynein (as well as their target components ZW10 and ROD), and the spindle checkpoint proteins (such as Mad1, Mad2, BubR1 and Cdc20). These proteins assemble on the kinetochore in high concentrations in the absence of microtubules; however, the higher the number of MTs anchored to the kinetochore, the lower the concentrations of these proteins. At metaphase, CENP-E, Bub3 and Bub1 levels diminish by a factor of about three to four as compared with free kinetochores, whereas dynein/dynactin, Mad1, Mad2 and BubR1 levels are reduced by a factor of more than 10 to 100.
  Whereas the spindle checkpoint protein levels present in the outer plate diminish as MTs anchor, other components such as EB1, APC and proteins in the Ran pathway (RanGap1 and RanBP2) associate to kinetochores only when MTs are anchored. This may belong to a mechanism in the kinetochore to recognize the microtubules' plus-end (+), ensuring their proper anchoring and regulating their dynamic behavior as they remain anchored.
  A 2010 study used a complex method (termed "multiclassifier combinatorial proteomics" or MCCP) to analyze the proteomic composition of vertebrate chromosomes, including kinetochores. Although this study does not include a biochemical enrichment for kinetochores, obtained data include all the centromeric subcomplexes, with peptides from all 125 known centromeric proteins. According to this study, there are still about one hundred unknown kinetochore proteins, doubling the known structure during mitosis, which confirms the kinetochore as one of the most complex cellular substructures. Consistently, a comprehensive literature survey indicated that there had been at least 196 human proteins already experimentally shown to be localized at kinetochores.