O

o-o items o-o are in brief format :
o-o operons
o-o opsonins
o-o opsonization

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| 0 Guide-Glossary

operons

In prokaryotes, operons are defined as groups of genes transcribed under the control of a single operator gene.

The operon comprises a functionally integrated genetic unit for the control of gene expression in bacteria. The operon comprises one or more genes together with an adjacent* promoter (activator or repressor) and an operator that controls expression through interaction with a regulator protein.

Control of prokaryotic gene expression is brought about by control of the rate of transcriptional initiation by two DNA promoter sequence elements. Regulatory accessory proteins alter the activity of RNA polymerase at a given promoter by affecting the ability of RNA polymerase to recognize start-sites. These regulatory proteins can act both positively (activators) and negatively (repressors).

In bacteria, regulons comprise several operons, and are global regulatory systems that participate in pleiotropic regulatory domains.

(* in eukaryotes, a regulon is defined as a group of non-contiguous genes)

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opsonization

Opsonins bind to target antigens, marking their carrier for phagocytosis. Opsonin molecules include IgG antibodies and components of the complement system (C3b, C4b, and iC3b).

Phagocytic cells express opsonin-binding receptors, and opsonization promotes phagocytosis in addition to inducing increasing the expression of complement receptors on phagocytes.

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