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 (By similarity). Forms a disulfide-linked heterodimer (via 2B domains) with KRT5 (via 2B domains) (By similarity). Forms a heterodimer with KRT1; the interaction is more abundant in the absence of KRT5 (By similarity). Interacts with TRADD and with keratin filaments (By similarity). Associates with other type I keratins (By similarity). Interacts with EPPK1 (By similarity). Interacts with KLHL24 (By similarity). Expressed in both as a filamentous pattern. 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. 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.