Histone H3-like variant which exclusively replaces conventional H3 in the nucleosome core of centromeric chromatin at the inner plate of the kinetochore. Required for recruitment and assembly of kinetochore proteins; mitotic progression and chromosome segregation. May serve as an epigenetic mark that propagates centromere identity through replication and cell division. Required for functional chromatin architecture at the yeast 2-micron circle partitioning locus and promotes equal plasmid segregation. {ECO:0000269|PubMed:10454560; ECO:0000269|PubMed:10499801; ECO:0000269|PubMed:10891506; ECO:0000269|PubMed:11063678; ECO:0000269|PubMed:11606525; ECO:0000269|PubMed:15590827; ECO:0000269|PubMed:16207811; ECO:0000269|PubMed:16966420; ECO:0000269|PubMed:7698647; ECO:0000269|PubMed:9584087; ECO:0000269|PubMed:9741625}.