PROSITE documentation PDOC00823

S-layer homology (SLH) domain profile

S-layers are paracrystalline mono-layered assemblies of (glyco)proteins which coat the surface of bacteria [1,2]. Several S-layer proteins and some other cell wall proteins contain one or more copies of a domain of about 50-60 residues, which has been called SLH (for S-layer homology). Although it was originally proposed that SLH domains bind to peptidoglycan, it is now evident that pyruvylated secondary cell wall polymers (SCWPs), which are either teichoic acids, teichuronic acids, lipoteichoic acids or lipoglycans, serve as the anchoring structures for SLH motifs in the Gram-positive cell wall [2,4]. However, the study of S-layer protein SbpA of Bacillus sphaericus revealed that SLH motifs are not sufficient for specific binding to SCWPs. Thus, the molecular basis explaining SLH affinity and specificity of interaction with cell wall polymers are not completely elucidated [5].

Some proteins known to contain SLH motif(s) are listed below:

• Bacillus anthracis sterne S-layer protein Sap (3 copies).
• Bacillus anthracis sterne 9131 S-layer protein EA1 (3 copies).
• Bacillus licheniformis strain NM 105 S-layer protein NM 105 (3 copies).
• Bacillus stearothermophilus PV72/p2 S-layer protein SbsB (3 copies).
• Bacillus sphaericus CCM 2177 S-layer protein SbpA (3 copies).
• Brevibacillus choshinensis strain HPD31 S-layer protein (HWP) (2 copies).
• Brevibacillus brevis strain 47 middle cell wall protein (MWP) (2 copies).
• Clostridium thermocellum NCIB 10682 S-layer protein SlpA (2 copies).
• Thermoanaerobacter kivui DSM 2030 S-layer glycoprotein (2 copies).
• Thermus thermophilus strain HB8 S-layer protein P100 (1 copy).
• Bacillus circulans Keratanase (3 copies).
• Bacillus sp. strain KSM-635 endoglucanase (3 copies).
• Bacillus sp. strain XAL601 amylopullulanase AapT (3 copies).
• Thermoanaerobacter saccharolyticum endoxylanase XynA (2 copies).
• Thermoanaerobacterium sp. strain JW/SL-YS 485 endoxylanase XynA (3 copies).
• Thermoanaerobacter thermosulfurogenes amylopullulanase (gene amyB) (3 copies).
• Thermoanaerobacter thermosulfurogenes endoxylanase XynA (3 copies).
• Thermoanaerobacter thermosulfurogenes polygalacturonase PglA (3 copies).
• Cellulomonas fimi mannanase Man26A (3 copies).
• Acetivibrio cellulolyticus cellulosomal scaffoldin protein ScaC (3 copies).
• Clostridium josui endoglucanase (gene celA) (3 copies).
• Clostridium thermocellum cellulosomal scaffoldin dockerin binding protein SdbA (3 copies).
• Clostridium thermocellum cell surface glycoprotein OlpB (3 copies).
• Clostridium thermocellum endoglucanase EngE (3 copies).
• Clostridium thermocellum exoglucanase XynX (3 copies).
• Synechococcus sp. PCC7942 outer membrane protein SomA (1 copy).
• Thermotoga maritima outer membrane protein Omp α (1 copy).

The profile we developed covers the entire SLH domain.