J. Freund et al., STABILITY AND PROTEOLYTIC DOMAINS OF NEF PROTEIN FROM HUMAN-IMMUNODEFICIENCY-VIRUS (HIV) TYPE-1, European journal of biochemistry, 221(2), 1994, pp. 811-819
Proteolytic experiments in conjunction with H-1-NMR spectroscopy show
that the Nef (negative factor) protein from human immunodeficiency vir
us type 1 probably consists of two main domains, the N-terminal anchor
domain at amino acid positions 2-65 and the C-terminal core domain at
positions 66-206. The N-terminal domain is likely to be located at th
e surface of the protein, while the C-terminal domain has a compactly
folded core and is stable in the absence of the anchor domain. It is c
onceivable that the core domain represents a functional domain of the
Nef protein, activated after the removal of the membrane anchor by the
human-immunodeficiency-virus protease or cellular proteases. Nef is s
table at pH 5-12 and denatures at 317-322 K. The Nef protein remains i
n its native conformation in dimethyl-sulfoxide/water mixtures up to 3
5% (by vol.), and in acetonitrile/water up to 14% (by vol.). Nef refol
ds spontaneously after denaturation with urea or guanidinium hydrochlo
ride. The H-1-NMR parameters and pK(a) values of five of the nine hist
idine residues and one of the seven tyrosine residues were determined
and were found in four cases to be typical for residues which are not
located in the interior of the protein.