Carboxymethylation of the human estrogen receptor ligand-binding domain-estradiol complex: HPLC/ESMS peptide mapping shows that cysteine 447 does not react with iodoacetic acid.

Experiments were carried out to determine the degree of solvent and reagent accessibility of the cysteines in the ligand-binding domain of the human estrogen receptor (hER LBD). The cysteine residues were alkylated when human ER LBD was present in its ligand (estradiol)-bound conformation. Direct electrospray ionization mass spectrometry (ESMS) as well as liquid chromatography coupled with ESMS, and matrix-assisted laser ionization desorption time-of-flight mass spectrometry were used to determine the location and the yield of the derivatized residues after proteolysis with trypsin.

Insect immunity. The inducible antibacterial peptide diptericin carries two O-glycans necessary for biological activity.

A bacterial challenge of larvae of the dipteran insect Phormia terranovae induces the rapid synthesis of diptericin, an antibacterial polypeptide, previously characterized at the amino acid level and indirectly by cDNA cloning studies. This 82-residue polypeptide consists of an N-terminal proline-rich domain and a central and C-terminal glycine-rich domain. Using liquid chromatography coupled to electrospray ionization-mass spectrometry, we demonstrate here that this molecule is more complex than anticipated and carries two O-substitutions on threonine residues, one in the proline-rich domain (residue 10) and one in the glycine-rich domain (residue 54).

Novel inducible antibacterial peptides from a hemipteran insect, the sap-sucking bug Pyrrhocoris apterus.

Insects belonging to the recent orders of the endopterygote clade (Lepidoptera, Diptera, Hymenoptera and Coleoptera) respond to bacterial challenge by the rapid and transient synthesis of a battery of potent antibacterial peptides which are secreted into their haemolymph. Here we present the first report on inducible antibacterial molecules in the sap-sucking bug Pyrrhocoris apterus, a representative species of the Hemiptera, which predated the Endoptergotes by at least 50 million years in evolution. We have isolated and characterized from immune blood of this species three novel peptides or polypeptides: (i) a 43-residue cysteine-rich anti-(Gram-positive bacteria) peptide which is a new member of the family of insect defensins; (ii) a 20-residue proline-rich peptide carrying an O-glycosylated substitution (N-acetylgalactosamine), active against Gram-negative bacteria; (iii) a 133-residue glycine-rich polypeptide also active against Gram-negative bacteria.

A novel inducible antibacterial peptide of Drosophila carries an O-glycosylated substitution.

One of the facets of the host defense of higher insects is the rapid and transient synthesis, following bacterial challenge or trauma, of a battery of potent antibacterial peptides (Steiner, H., Hultmark, D., Engström, A.

A novel insect defensin mediates the inducible antibacterial activity in larvae of the dragonfly Aeschna cyanea (Paleoptera, Odonata).

The injection of low doses of bacteria into the aquatic larvae of dragonflies (Aeschna cyanea, Odonata, Paleoptera) induces the appearance in their hemolymph of a potent antibacterial activity. We have isolated a 38-residue peptide from this hemolymph which is strongly active against Gram-positive bacteria and also shows activity against one of the Gram-negative bacteria which was tested. The peptide is a novel member of the insect defensin family of inducible antibacterial peptides, which had so far only been reported from the higher insect orders believed to have evolved 100 million years after the Paleoptera.