Polypeptides and Proteins
Peptides and proteins
peptides are common in plants, animals, bacteria etc. Many peptides have hormonal activity in animals
oxytocin
vasopressin
Microbial peptide antibiotics
e.g., benzyl penicillin, cephalosporin
many have D-amino acids, but the L-amino acids seem to be incorporated better, suggesting that the configuration is changed after the fact.
the two above inhibit cell wall formation in bacteria
bleomycin A2 has pronounced antitumor activity
Fungal peptides
best known from the genus Amanita
two series phallotoxins and amatoxins
Phallotoxins
toxic, attack liver cells in people. alter membranes, interact with actin filaments,
Amatoxins
such as α-amanatin, which inhibits RNA-polymerase II in the cell nucleus. slow acting, but extremely poisonous to people
Phytotoxins produced by bacteria and/or fungi
many pathogenic fungi and bacteria
help to break down the host tissue and release nutrients
fungal compounds generally more specific in activity than the bacterial ones
often combinations, e.g., fusaric acid and lycomarasmin in tomatoes from Fusarium oxysporum.
tabtoxin produces light-dependent chlorosis in the plants from Pseudomonas syringae
rhizobitoxin produces chlorosis in soybeans attacked by the root-nodulating organism Rhizobium japonicum. irreversible inhibitor of ethylene production.
Opines
infection with Agrobacterium results in formation of tumors and opines. These are unique products of infected cells.
Blue-green algae
many blue green algae make highly toxic peptides
Siderophores
many peptides are made by bacteria and fungi that scavenge iron and other minerals from the environment
Higher plant peptides
Phytochelatins
reduce heavy metal toxicity
Lectins
Plant proteins
plant phytohemoglobins
Toxic peptides
Lectins
these compounds agglutinate cells, usually animal cells. They often interact more or less specifically with sugar residues on the cell surface
common in Fabaceae (Leguminosae) and Euphorbiaceae
especially toxic
Abrus precatorius
Robinia pseudoacacia
Ricinus communis
Phoradendron and Viscum (Loranthaceae or Viscaceae)
Nitrogen fixing interactions
interactions of bacteria and host cells highly specific ... involve binding via lectins
Plants with Peptides and Proteins
© David S. Seigler, Integrative Biology 425, Plant Secondary Metabolism, Department of Plant
Biology, 265 Morrill Hall, 505 S. Goodwin Ave., University of Illinois, Urbana, Illinois 61801, USA.
217-333-7577. seigler@life.uiuc.edu.
