The signal-recognition particle. The signal-recognition particle (SRP) consists of six proteins and one 300-nucleotide RNA molecule. The RNA has a complex structure with many double-helical stretches punctuated by single-stranded regions, shown as circles.
[Information from H. Lodish et al., Molecular Cell Biology, 5th ed. (W. H. Freeman and Company, 2004). Data from K. Strub et al., Mol. Cell Biol. 11:3949–3959, 1991, and S. High and B. Dobberstein, J. Cell Biol. 113:229–233, 1991.]