Required for the formation of keratin intermediate filaments in the basal epidermis and maintenance of the skin barrier in response to mechanical stress (PubMed:11408584). Regulates the recruitment of Langerhans cells to the epidermis, potentially by modulation of the abundance of macrophage chemotactic cytokines, macrophage inflammatory cytokines and CTNND1 localization in keratinocytes (PubMed:19267394). Heterodimer of a type I and a type II keratin. Heterodimer with type I keratin KRT25 leading to the formation of keratin intermediate filament (KIF) network (By similarity). Forms a heterodimer (via 2B domains) with KRT14 (via 2B domains) (PubMed:24940650). Interacts with PLEC isoform 1C, when in a heterodimer with KRT14 (PubMed:24940650). Interacts with TCHP (By similarity). Interacts with EPPK1 (PubMed:18285451). Interacts with AMELX (PubMed:12657653). Expressed in the corneal epithelium (at protein level) (PubMed:26758872, PubMed:11408584). Expressed in the epidermis of the ear (at protein level) (PubMed:24751727). Expressed in the basal and spinous layers of the skin at birth (at protein level) (PubMed:11408584). Expressed in basal layer cells of the stratified squamous epithelia at 15.5 dpc (PubMed:29518391). Expressed in the skin after birth (PubMed:29518391). Expressed in ameloblasts at the cervical and apical mid-regions of mandibular molars at birth, abundance at the apical mid-region significantly increases at P1, and is maintained throughout enamel development until P9 when ameloblasts start losing their integrity (PubMed:12657653). Expressed in ameloblasts at the incisal region of mandibular molars at P3 (PubMed:12657653). Expressed at the Tomes' processes of ameloblasts at the incisal region at P5 (PubMed:12657653). Expression at the incisal region decreased at P7 and P9 (PubMed:12657653). Weakly expressed in the spinous and granular layers of the tongue at P20 (PubMed:32758484). Phosphorylated by CDK1, AURKB and Rho-kinase, phosphorylation is regulated by the cell cycle (PubMed:29518391). Thr-24 phosphorylation, mediated by CDK1, peaks during prometaphase or metaphase cells with phosphorylated filamentous structures evident throughout the cytoplasm during early mitosis (PubMed:29518391). CDK1 phosphorylates Thr-24 in mitotic cells at the site of injury (PubMed:29518391). O-glycosylated. Paws are frequently denuded and epidermis loses contact with the dermis following the mechanical stress of birth, mice die within 1 hour of birth (PubMed:11408584). Tongue cytolysis is evident following birth even before the first milk uptake (PubMed:11408584). Complete loss of keratin filaments in the basal layer, leading to cleavage of the epidermis in the subnuclear cytoplasm just superficial to the hemidesmosomes (PubMed:11408584). Increase in Krt6 expression in the spinous and lower granular layers as well as weakly in basal layer of the blistering roof of cytolyzing cells at birth (PubMed:11408584). Decrease in Krt14 expression in the skin following birth (PubMed:11408584). Increase in Langerhans cells in the epidermis (PubMed:19267394). Decrease in Ctnnd1/p120 localization to the plasma membrane and adherens junctions of basal keratinocytes (PubMed:19267394). Increase in the cytokines Cxcl16, Ccl2, Ccl19 and Ccl20 in the epidermis at birth (PubMed:19267394). There are two types of cytoskeletal and microfibrillar keratin: I (acidic; 40-55 kDa) and II (neutral to basic; 56-70 kDa). Belongs to the intermediate filament family.