Histone H3-like nucleosomal protein that is specifically found in centromeric nucleosomes (PubMed:14563550). Replaces conventional H3 in the nucleosome core of centromeric chromatin at the inner plate of the kinetochore. The presence of CENPA subtly modifies the nucleosome structure and the way DNA is wrapped around the nucleosome and gives rise to protruding DNA ends that are less well-ordered and rigid compared to nucleosomes containing histone H3. May serve as an epigenetic mark that propagates centromere identity through replication and cell division (By similarity). Required for recruitment and assembly of kinetochore proteins, and as a consequence required for progress through mitosis, chromosome segregation and cytokinesis (PubMed:15870271). Component of centromeric nucleosomes, where DNA is wrapped around a histone octamer core. The octamer contains two molecules each of H2A, H2B, CENPA and H4 assembled in one CENPA-H4 heterotetramer and two H2A-H2B heterodimers. CENPA modulates the DNA-binding characteristics of nucleosomes so that protruding DNA ends have higher flexibility than in nucleosomes containing conventional histone H3. Localizes exclusively in the kinetochore domain of centromeres. Occupies a compact domain at the inner kinetochore plate stretching across 2 thirds of the length of the constriction but encompassing only one third of the constriction width and height. Present in all interphase cells with a punctate pattern in the nucleus. Aligned along the metaphase plate in metaphase cells and becomes concentrated at the poles in anaphase cells (at protein level). Belongs to the histone H3 family.