Related Experiment Video
Updated: Jun 10, 2026

Isolation of Lipoprotein Particles from Chicken Egg Yolk for the Study of Bacterial Pathogen Fatty Acid Incorporation into Membrane Phospholipids
Published on: May 15, 2019
The structure and function of serum opacity factor: a unique streptococcal virulence determinant that targets
Harry S Courtney1, Henry J Pownall
1Veterans Affairs Medical Center and Department of Medicine, University of Tennessee Health Science Center, 1030 Jefferson Avenue, Memphis, TN 38104, USA. hcourtney@uthsc.edu
Abstract:
Serum opacity factor (SOF) is a virulence determinant expressed by a variety of streptococcal and staphylococcal species including both human and animal pathogens. SOF derives its name from its ability to opacify serum where it targets and disrupts the structure of high-density lipoproteins resulting in formation of large lipid vesicles that cause the serum to become cloudy. SOF is a multifunctional protein and in addition to its opacification activity, it binds to a number of host proteins that mediate adhesion of streptococci to host cells, and it plays a role in resistance to phagocytosis in human blood. This article will provide an overview of the structure and function of SOF, its role in the pathogenesis of streptococcal infections, its vaccine potential, its prevalence and distribution in bacteria, and the molecular mechanism whereby SOF opacifies serum and how an understanding of this mechanism may lead to therapies for reducing high-cholesterol concentrations in blood, a major risk factor for cardiovascular disease.
Related Concept Videos
Formation of Lipopolysaccharides
Determinants of Bacterial Pathogenicity and Virulence
Staphylococcal Skin Infections
Lipid-derived Compounds in the Human Body
Fat-soluble Vitamins
Fat-soluble vitamins, including vitamins A, D, E, and K, are required in minimal quantities, but their deficiencies can lead to severely abnormal physiological conditions. For example, vitamin A deficiency can cause night blindness, dry skin, delayed...
Outer Layers of the Cell Envelope
Streptococcal Pharyngitis

