Structure–activity relationship studies of gomesin: Importance of the disulfide bridges for conformation, bioactivities, and serum stability

Abstract

Gomesin is an antimicrobial peptide isolated from hemocytes of the Brazilian spider Acanthoscurria gomesiana that contains two disulfide bridges Cys(2-15)/Cys(6-11) and presents a beta-hairpin structure. To investigate the role of the disulfide bridges on gomesin conformation, bioactivities, and serum stability, structure-activity relationship (SAR) studies were conducted. Initially, gomesin and variants lacking one or both disulfide bridges were synthesized. CD studies showed that the gomesin structure is very rigid independently of the solvent environment. On the other hand, the linearized analogues adopted secondary structures according to the environment, while the monocyclic disulfide-bridged peptides had a tendency to adopt a turn structure. The absence of one or both bridges resulted in a decrease in the antimicrobial and hemolytic activities. In addition, serum stability studies revealed that, contrasting to gomesin that was stable even after 48 h of incubation, the linearized analogues were rapidly degraded. The replacement of the disulfide bounds by lactam bridges led to monocyclic and bicyclic compounds. SAR studies indicated that the monocyclic lactam-bridged analogues tend to assume a alpha-helical structure being less potent, hemolytic, and serum stable than the wild-type gomesin. On the other hand, the bicyclic lactam/disulfide-bridged analogues displayed a similar conformation and degradation kinetics identical to gomesin. However, the antimicrobial activity appeared to be dependent on the lactam bridge position and size. These findings indicated that (i) the secondary structure plays a pivotal role for the full activity of gomesin; (ii) the antimicrobial and hemolytic activities of gomesin are correlated events; (iii) while at least one of the disulfide bridges is needed for the maintenance of a significant antimicrobial activity of gomesin, both bridges are required for high serum stability and optimal conformation; and finally (iv) the best analogue obtained was the bicyclo (2-15,6-11)[Glu2, Cys(6,11), Lys15]-Gm since it is as stable and potent as gomesin.

The role of disulfide bridges in the 3-D structures of the antimicrobial peptides gomesin and protegrin-1: a molecular dynamics study

“…These subtle differences deserve experimental investigation. Indeed, Fazio et al (2006) have already studied several gomesin variants with respect to structure-activity relationship and the importance of disulfide bridges for conformation and bioactivity; however, the four cysteines were not replaced by tyrosine residues in any of the fourteen mutants studied by them. Tables 3 and 4 show the peak maximum values or the shoulders in the Ramachandran angle histograms for gomesin/gomy4 and protegrin-1/proty4, respectively.…”

“…Gomesin is active against bacteria, fungi and parasites. It is structurally very similar to protegrin-1, as well as other peptides such as androctonin, polyphemusins, and tachyplesin I, and it adopts a well-defined β-hairpin-like structure (Fahrner et al, 1996;Fazio et al, 2006;Lam et al, 2006). Protegrin-1 is also an antimicrobial peptide, active against several Gram-positive and Gram-negative bacteria, fungi, and HIV-1.…”

“…The impact of such a challenging problem has motivated numerous academic and pharmaceutical industry research groups to develop new drugs capable of dealing with the adaptation strategy (namely the selection of organisms adapted to some specific medium) that these organisms develop over time (Prates and Bloch Júnior, 2000;Fazio et al, 2006;Ramamoorthy et al, 2006;Che et al, 2008).…”

Bauhinia Bauhinioides Kallikrein Inhibitor Fragments with Bradykinin-Like Activities

“…Peptides (Table 1) were manually synthesized by using the Boc-strategy [4]. After RP-HPLC purification, they were characterized by LC-ESI-MS. Stomach fundus was isolated from mouse and mounted into organ bath containing modified Krebs-Ringer solution at 37°C (pH 7.4).…”

Estudo da relação estrutura-atividades e de propriedades do Hb40-61a, uma hemocidina sintética

“…Muitos peptídeos com ação antibiótica apresentam certo grau de toxicidade a células de mamíferos, tais como a melitina (OREN; SHAI, 1997), a protegrina I (STORICI; ZANETTI, 1993), a indolicidina (SELSTED et al, 1992) e a gomesina (FÁZIO et al, 2006). Esta toxicidade, na maioria das vezes, é avaliada por meio do ensaio hemolítico.…”