Science et technologie vétérinaires

Bacterial Protein Secretion with Particular Emphasis to Toxins

Abstract

Yitbarek Habtamu, Jaleta Shukab, and Fanos Tadessef

Bacterial cells must transport proteins across their membranes for the biogenesis of membranes and cell walls, motility and nutrient
scavenging and uptake, and is also involved in pathogenesis and symbiosis. The translocase is an impressively dynamic nanomachine that is
the central component which catalyses trans-membrane crossing. This complex, multi-stage reaction involves a cascade of inter and intramolecular
interactions that select, sort and target polypeptides to the membrane, and in addition, transport through the outer membrane
requires ATP or other sources of energy to promote the movement of these polypeptides across or their lateral escape and integration into
the phospholipid bilayer, with high fidelity and efficiency. Here, the review addresses the structure and function of the translocase
nanomachine and different mechanisms of protein secretion and their transport. The general secretion Sec and twin arginine translocation
pathways are the bacterial secretion systems most commonly used to transport proteins across the cytoplasmic membrane. Often, Sec or Tat
systems transport unfolded and folded proteins first to the periplasmic space in Gram negative bacteria, where they are processed to obtain
their final three-dimensional structure, before being transported across the outer membrane. There are different path ways in which some
are sec dependent and others sec independent. Secretion types II, IV, V and VII are sec-dependent pathways while others like type I, III and VI
pathways are sec-independent. Secreted proteins can play many roles in promoting bacterial virulence, from enhancing attachment
to eukaryotic cells, to scavenging resources in an environmental niche, to directly intoxicating target cells and disrupting their functions.
Therefore, the study of protein secretion systems will be an important focus in the field of bacterial pathogenesis, and virulence for the
characterization of various bacterial pathogens.