The Crithidia fasciculata KAP1 gene encodes a highly basic protein associated with kinetoplast DNA.

The Crithidia fasciculata KAP1 gene encodes a small basic protein (p21) associated with kinetoplast DNA. The p21 protein has a nine amino acid cleavable presequence closely related to those of several other proteins targeted to the kinetoplast and binds non-specifically to kinetoplast minicircle DNA. The p21 protein also has a calculated pI of 13 with two amino acids (lysine and alanine) accounting for more than 50% of the residues and with 25 out of 28 lysine residues contained in the C-terminal half of the protein. Immunolocalization of p21 shows that the protein is found exclusively in the kinetoplast with a localization distinctly different from the antipodal localization of kinetoplast DNA topoisomerase and DNA polymerase. The KAP11 gene is a single copy gene and the KAP1 mRNA is present at a constant level throughout the cell cycle. This highly basic protein may play a role in the condensation or segregation of the kinetoplast DNA.