MSCRAMM (acronym for "microbial surface components recognizing adhesive matrix molecules") adhesin proteins mediate the initial attachment of bacteria to host tissue, providing a critical step to establish infection.
Examples include
protein A
Protein A is a 42 kDa surface protein originally found in the cell wall of the bacteria ''Staphylococcus aureus''. It is encoded by the ''spa'' gene and its regulation is controlled by DNA topology, cellular osmolarity, and a two-component system ...
,
clumping factor A Clumping factor A, or ClfA, is a virulence factor from ''Staphylococcus aureus
''Staphylococcus aureus'' is a Gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, freque ...
(ClfA),
fibronectin binding protein A Fibronectin binding protein A (FnBPA) is a ''Staphylococcus aureus'' MSCRAMM cell surface-bound protein that binds to both fibronectin and fibrinogen.
It is an Bacterial adhesin, adhesin which enables ''Staphylococcus aureus'' (''S. aureus'') to ad ...
(FnbpA) from ''
Staphylococcus aureus
''Staphylococcus aureus'' is a Gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often positive ...
'',
SdrG from ''
Staphylococcus epidermidis
''Staphylococcus epidermidis'' is a Gram-positive bacterium, and one of over 40 species belonging to the genus '' Staphylococcus''. It is part of the normal human microbiota, typically the skin microbiota, and less commonly the mucosal microbio ...
'',
M protein from ''
Streptococcus pyogenes
''Streptococcus pyogenes'' is a species of Gram-positive, aerotolerant bacteria in the genus ''Streptococcus''. These bacteria are extracellular, and made up of non-motile and non-sporing cocci (round cells) that tend to link in chains. They are ...
'', and
protein G
Protein G is an immunoglobulin-binding protein expressed in group C and G Streptococcal bacteria much like Protein A but with differing binding specificities. It is a ~60-kDA (65 kDA for strain G148 and 58 kDa for strain C40) cell surface prote ...
in other ''Streptococcus'' species. All of these MSCRAMMs bind to fibrinogen except protein A, that binds
IgG
Immunoglobulin G (Ig G) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG ...
, but also other targets for MSCRAMMs are known, such as fibronectin. Protein M binds to the Fc region of certain
antibodies
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
.
The MSCRAMMs have mainly been studied in
Gram positive
In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall.
Gram-positive bact ...
pathogens and are promising drug targets.
The monoclonal antibody
tefibazumab
Tefibazumab (named Aurexis but not approved) is a humanized monoclonal antibody for the treatment of severe infections with '' Staphylococcus aureus''. Possible indications include the treatment of ''S. aureus'' in a phase 2a patients with cystic ...
targets ClfA and has been tested in a
phase II trial.
''Staphylococcus aureus''
An example for MSCRAMMs is ''S. aureus''. On its surface, protein A is expressed, which binds to the Fc region of IgG antibodies (the default antibody type, dealing with bacterial and viral infections). This has an antiphagocytic effect, i.e. macrophages cannot "see" these bacteria as easily as if they were correctly opsonised by antigen. Also, ''S. aureus'' expresses fibronectin-binding proteins, which promote binding to mucosal cells and tissue matrices. This protein is also referred to as clumping factor.
References
Bacterial proteins
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