Identification and characterization of a second extracellular collagen-like protein made by group A Streptococcus: Control of production at the levelof translation
S. Lukomski et al., Identification and characterization of a second extracellular collagen-like protein made by group A Streptococcus: Control of production at the levelof translation, INFEC IMMUN, 69(3), 2001, pp. 1729-1738
A recent study found that group A Streptococcus (GAS) expresses a cell surf
ace protein with similarity to human collagen (S, Lukomski, K. Nakashima, I
. Abdi, V, J, Cipriano, R. M, Ireland, S. R, Reid, G, G, Adams, and J, M. M
usser, Infect. Immun, 68:6542-6553, 2000), This streptococcal collagen-like
protein (Scl) contains a long region of Gly-X-X motifs and was produced by
serotype M1 GAS strains. In the present study, a second member of the scl
gene family was identified and designated scl2. The Scl2 protein also has a
collagen-like region, which in M1 strains is composed of 38 contiguous Gly
X-X triplet motifs, The scl2 gene was present in all 50 genetically divers
e GAS strains studied. The Scl2 protein is highly polymorphic, and the numb
er of Gly-X-X motifs in the 50 strains studied ranged from 31 in one seroty
pe M1 strain to 79 in serotype M28 and M77 isolates. The scl1 and scl2 gene
s were simultaneously transcribed in the exponential phase, and the Sd prot
eins were also produced. Scl1 and Scl2 were identified in a cell-associated
form and free in culture supernatants, Production of Scl1 is regulated by
Mga, a positive transcriptional regulator that controls expression of sever
al GAS virulence factors. In contrast, production of Scl2 is controlled at
the level of translation by variation in the number of short-sequence penta
nucleotide repeats (CAAAA) located immediately downstream of the GTG (Val)
start codon. Control of protein production by this molecular mechanism has
not been identified previously in GAS. Together, the data indicate that GAS
simultaneously produces two extracellular human collagen-like proteins in
a regulated fashion.