The nonhelical tail domain is involved in promoting KRT5-KRT14 filaments to self-organize into large bundles and enhances the mechanical properties involved in resilience of keratin intermediate filaments in vitro. Heterotetramer of two type I and two type II keratins (PubMed:22705788). Forms a disulfide-linked heterodimer (via 2B domains) with KRT5 (via 2B domains) (PubMed:22705788, PubMed:24940650). Forms a heterodimer with KRT1; the interaction is more abundant in the absence of KRT5 (PubMed:11408584). Interacts with PLEC isoform 1C, when in a heterodimer with KRT5 (PubMed:24940650). Interacts with TRADD and with keratin filaments (PubMed:16702408). Associates with other type I keratins (By similarity). Interacts with EPPK1 (PubMed:18285451). Interacts with KLHL24 (By similarity). Expressed in both as a filamentous pattern. Expressed in the corneal epithelium (at protein level) (PubMed:26758872). Expressed in the basal layer of the epidermis and the outer root sheath of hair follicles (at protein level) (PubMed:11408584). Expressed in the epithelial basal layer in the tail epidermis (PubMed:2433272). Expressed in the parabasal cell row, basal cell layer, and suprabasal epithelial layer of the tongue (PubMed:2433272). Expressed in the epithelial cells of the tongue and palate at 17 dpc (PubMed:2433272). Expressed in ameloblasts at the periphery and 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). A disulfide bond is formed between rather than within filaments and promotes the formation of a keratin filament cage around the nucleus. Ubiquitinated by the BCR(KLHL24) E3 ubiquitin ligase complex. Increase in CXCL16 abundance in the epidermis at 2 days of age. 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.