Fibronectin receptors from Staphylococcus aureus

Fibronectin which is recognized for its ability to mediate
substrate adhesion of eucaryotic cells has also
been shown to bind to Staphylococcus aureus (Kuusela,
P. (1978) Nature (Lond)2 76, 718-720). A further characterization
of the interaction of fibronectin with
staphylococci is presented here. The binding of 1251-
fibronectin to S. aureus, strain Cowan 1, is specific,
time-dependent, functionally irreversible, and occurs
to both live and heat-killed cells. Furthermore, staphylocci
may be saturated with fibronectin at a level which
suggests the presence of 250 receptors/cell. A lysate
produced by digestion of staphylococcal cells with a
bacteriolytic enzyme (lysostaphin) inhibited the binding
of 125I-fibronectin to bacteria. The lysate was depleted
of its inhibitory activity by passage through a
column of Sepharose substituted with fibronectin. The
inhibitory activity was destroyed when the lysate was
incubated with trypsin or pronase, and a lysate prepared
from trypsin-treated cells did not have inhibitory
activity. These data suggest that the inhibitory activity
of the lysate is due to solubilized surface proteins acting
as receptors for fibronectin. Staphylococcal mutants
that selectively had lost protein A or fibronectin receptors
could be isolated, which suggests the presence of
fibronectin receptors distinctly different from protein
A. Externally 125 I-labeled proteins from the different
mutants were analyzed by affinity chromatography on
fibronectin-Sepharose followed by gel electrophoresis.
The fibronectin receptor was tentatively identified as
a protein with an apparenMt , = 18,000. This component
was found in fibronectin-binding strains but was absent
in strains deficient in fibronectin receptors.