Solution structures were not computed for TPF4 and TPA4.

Solution and micelle-bound structures of tachyplesin I and its active aromatic linear derivatives.

Tachyplesin is a potent antimicrobial peptide isolated from the hemocytes of the
horseshoe crab, Tachypleus tridentatus. Previous studies have shown that the
17-residue peptide has an intrinsic amphipathic structure conferred by two
antiparallel beta-sheets held rigidly by two disulfide bonds. Taking its short
length into account and the potential of such a small polypeptide to take on
multiple conformational states, one may assume that the disulfide bonds are
relevant determinants of function. However, in order to gain a global
perspective on the tolerance of cysteine residues in tachyplesin to amino acid
substitutions, a series of linear peptides have been synthesized and their
physicochemical properties analyzed. In these linear peptides, the cysteines
have been replaced with amino acids possessing different side-chain properties,
i.e., aliphatic hydrophobic (Ala, Leu, Ile, Val, and Met), aromatic hydrophobic
(Phe and Tyr), and acidic (Asp). Activity assays using natural and synthetic
membranes, and conformational measurements, highlight the subtle influence and
variability of the amino acid side-chain properties on peptide structure. While
an unequivocal interpretation of the results will have to await more refined
structural measurements, our results indicate that a rigidly held
disulfide-bonded beta-pleated sheet structure may not be absolutely essential
for antimicrobial activity. Furthermore, the results challenge the accepted
dogma of structure-activity relationships among antimicrobial peptides and
suggest that the maintenance of peptide hydrophobic-hydrophilic balance may be
a critical parameter, in addition to structure, in the design of peptides with
pharmaceutical relevance.

Rao AG.
Conformation and antimicrobial activity of linear derivatives of tachyplesin
lacking disulfide bonds.
Arch Biochem Biophys. 1999 Jan 1;361(1):127-34.

Conformation and antimicrobial activity of linear derivatives of tachyplesin lacking disulfide bonds.

The solution structure of tachyplesin I, which was isolated from membrane acid
extracts of the hemocytes from the Japanese horseshoe crab (Tachypleus
tridentatus), was determined by nuclear magnetic resonance (NMR) and distance
geometry calculation. Tachyplesin I takes an antiparallel beta-sheet structure
with a type-II beta-turn. Recently, among more than 20 synthetic peptides
associated with tachyplesin and its isopeptide (polyphemusin), we found that a
novel compound, which we designated as T22 ([Tyr5,12, Lys7]-polyphemusin II),
strongly inhibited the human immunodeficiency virus (HIV)-1-induced cytopathic
effect and viral antigen expression. The solution structure of T22 was
investigated using NMR, and its secondary structure was confirmed to be similar
to that of tachyplesin I. The anti-parallel beta-sheet structure and the
several amino-acid side chains on the plane of the beta-sheet of T22 are
thought to be associated with the expression of anti-HIV activity.

Tamamura H, Kuroda M, Masuda M, Otaka A, Funakoshi S, Nakashima H, Yamamoto N,
Waki M, Matsumoto A, Lancelin JM, et al.
A comparative study of the solution structures of tachyplesin I and a novel
anti-HIV synthetic peptide, T22 ([Tyr5,12, Lys7]-polyphemusin II), determined
by nuclear magnetic resonance.
Biochim Biophys Acta. 1993 May 13;1163(2):209-16.

A comparative study of the solution structures of tachyplesin I and a novel anti-HIV synthetic peptide, T22 ([Tyr5,12, Lys7]-polyphemusin II), determined by nuclear magnetic resonance.

Wild type, has two disulfide bridges (C3-C16, and C7-C12).
Wild Type, TPY4 and TPF4 adopt beta-hairpins.
TPY4, TPF4 and TPA4 are mutants in which the four Cyteine residues are
uniformly mutated to tyrosine, phenylalanine, and alanine, respectively.

Tachyplesin I In Dodecylphosphocholine Micelles

Solution Structure Of Tachyplesin I In H2o

Tachyplesin I Solution Structure In The Presence Of 300mm Dodecylphosphocholine Micelles

Tachyplesin I Wild Type Peptide Nmr Structure

Backbone and 1H assignments for Tachyplesin I, wild type

simulated annealing with complete cross validation

All experiments in water were done in these conditions.