Table 1.

The LLS/TPL motif in mouse and human type-II keratins

Keratin				L	L	S/T	P	L				[amino acids]
Epithelial cell keratins — “Soft” keratins
hK5	N	Q	S	L	L	T	P	L	N	L	Q	[149–159]
hK6a-c,e,fa	•	•	•	•	•	•	•	•	•	•	•	[140–150]
hK6hfa	•	•	•	•	•	•	•	•	H	•	•	[126–136]
mK6αb	•	•	•	•	•	•	•	•	•	•	•	[129–139]
mK6βb	•	•	N	•	•	•	•	•	•	V	•	[137–147]
hK4	•	•	•	•	•	•	•	•	H	V	E	[128–138]
mK4	•	•	•	•	•	•	•	•	Q	V	E	[123–133]
hK8	•	•	•	•	•	S	•	•	S	•	E	[68–78]
mK8	•	•	•	•	•	S	•	•	K	•	E	[74–84]
hK1	•	•	•	•	•	Q	•	•	•	V	•	[157–167]
Hair keratins — “Hard” keratins
hHb1, hHb6	•	E	•	•	•	•	•	•	•	•	E	[83–93]
hHb2	•	E	•	•	•	V	•	•	A	•	E	[97–107]
hHb3	•	E	•	•	•	•	•	•	•	•	E	[88–99]
hHb4	•	K	•	•	•	•	•	•	•	•	E	[142–152]
hHb5, mHb5c	•	E	•	•	•	•	•	•	•	•	E	[100–110]

Notably, the K5 P151→L mutation (Muller et al., 1998) involves the proline of the LLS/PL motif, and the K1 L160→P mutation (Chipev et al., 1992) creates a proline-directed kinase phosphorylation site (Ku et al., 2002). LLTPL is also present in sheep type II hair keratins (Powell et al., 1992), while LLSPL is also found in a frog type II keratin (Fouquet et al., 1988). 

h, human; m, mouse. For complete sequences see references (Knapp et al., 1986; Liao et al., 1997; Takahashi et al., 1998; Winter et al., 1998; Rogers et al., 2000). Dots indicate amino acid residues that are identical to the corresponding K5 residues. 

^aa-c, e, f, hf represent different isoforms of hK6. Human K6d is likely to have an identical LLTPL motif but its full sequence has not been reported. 

^bα, β correspond to mK6 isoforms. A recently discovered K6 isoform expressed in the mouse inner root sheath, K6irs, does not contain the LLTPL consensus sequence (Aoki et al., 2001). 

^cPubmed accession AAD01692.