Table 1.

Structure of HN peptide and role of individual amino acids.

Pos.	Amino acid	Function	Effect of amino acid substitution
N-TERM
1	Met (M)
2	Ala (A)
3	Pro (P)	Neuro-protection	Pro3 to Ala (P3A) – abrogates neuro-protective function
4	Arg (R)
HYDROPHOBIC CORE REGION
5	Gly (G)
6	Phe (F)	IGFBP-3 binding, Aβ binding	Phe6 to Ala (F6A) – abrogates IGFBP-3 binding
7	Ser (S)	Aβ protection	Ser7 to Ala (S7A) – abrogates cyto-protective and neuro-protective functions, and prevents dimerization
		Aβ binding
		Dimerization
8	Cys (C)	Neuro-protection	Cys8 to Ala (C8A) – abrogates neuro-protective function
		BAX, BAD, and tBID binding
9	Leu (L)	Neuro-protection	Leu9 to Arg (L9R) – Non-secretory, but retains function when added into the medium
		Secretion
		Dimerization	Leu9 Ala (L9A) – prevents dimerization and abrogates neuro-protective function
10	Leu (L)	Secretion	Leu10 to Asp (L10D) – abrogates secretion
			Leu10 to Arg (L10R) – abrogates secretion
11	Leu (L)	Secretion	Leu11 to Arg (L11R) – abrogates secretion
12	Leu (L)	Neuro-protection	Leu12 to Ala (L12A) – abrogates neuro-protective function
13	Thr (T)	Neuro-protection	Thr13 to Ala (T13A) – abrogates neuro-protective function
14	Ser (S)	Neuro-protection	Ser14 to Gly (S14G) increases cyto-protective potency over 1,000-fold. This isoform is active when monomeric
			Ser14 to D-Ser increases potency
			Ser14 to Ala (S14A) – abrogates neuro-protective function
15	Glu (E)
16	Ile (I)
17	Asp (D)
18	Leu (L)
C-TERM
19	Pro (P)	Aβ protection	Pro19 to Ala (P19A) – abrogates neuro-protective function
		Secretion	Pro19 to Arg (P19R) – abrogates secretion
20	Val (V)	Secretion	Val20 to Arg (V20A) – abrogates secretion
21	Lys (K)	IGFBP-3 binding	Lys21 to Ala (L21A) – blocks interaction at lower IGFBP-3 concentrations
22	Arg (R)	?Non-essential
23	Arg (R)	?Non-essential
24	Ala (A)	?Non-essential

Bolded: neuro-protective core domain (NPCD).