TABLE 4.

Summary of the roles of amino acids in LCAT interaction loop of apoA-I

The presumed functions proposed for the apoA-I residues are speculative and are based on a combination of both site-specific mutagenesis/functional studies and structural models of apoA-I reported in nHDL.

Amino acid in SF loop	Presumed function	Mutations/post-translational modification	Percentage of WT kcat (Vmax/Km)	Percentage of WT binding affinity
			%	%
Leu159	Structural	L159Ra	2	NDb
Arg160	Salt bridge	R160La	3–71	ND
His162	Salt bridge	H162Qa	16	ND
Pro165	Structural	P165Ra	38	ND
		P165A	42	36
Tyr166	Hydrogen bond/polar interaction	Y166F	12	23
		Y166E	77	109
		Y166N	91	140
		Y166A	38	22
		Y166YNO2c	55	5
Ser167	Hydrogen bond	S167A	29	54
Asp168	Salt bridge	D168A	13	19

^a Familial mutations associated with low HDL in plasma and LCAT activity (38, 39, 45, 46).

^b ND, not determined.

^c PTM identified in apoA-I from human aortic plaque (26, 35).