Immunological heterogeneity of Archeobacterial protein synthesis elongation factor Tu (EF-Tu).

Polyclonal antibodies were raised against the EF-Tu of the archaebacterium Sulfoobus solfataricus and cross-reactivities of EF-Tus of other, phylogenetically disparate archaebacteria were determined using Western blotting and ELISA. The results demonstrate a high degree of heterogeneity of archaebacterial Tu factors with recognition by S. solfataricus EF-Tu antibodies ranging from 48% to 1.5% that observed with the homologous antigen. The irnmunochemical relatedness between the heterologous and the cognate (Sulfolobus) antigens correlates satisfactorily with similarities in 16 S rRNA sequences, there being no recognition of eubacterial and eukaryotic factors by the S. solfataricus EF-Tu antibodies

Crystal structure of ribosomal protein L4 shows RNA-binding sites for ribosome incorporation and feedback control of the S10 operon

Ribosomal protein L4 resides near the peptidyl transferase center of the bacterial ribosome and may, together with rRNA and proteins L2 and L3, actively participate in the catalysis of peptide bond formation. Escherichia coli L4 is also an autogenous feedback regulator of transcription and translation of the 11 gene S10 operon. The crystal structure of L4 from Thermotoga maritima at 1.7 Å resolution shows the protein with an alternating α/β fold and a large disordered loop region. Two separate binding sites for RNA are discernible. The N–terminal site, responsible for binding to rRNA, consists of the disordered loop with flanking α–helices. The C–terminal site, a prime candidate for the interaction with the leader sequence of the S10 mRNA, involves two non-consecutive α–helices. The structure also suggests a C–terminal protein-binding interface, through which L4 could be interacting with protein components of the transcriptional and/or translational machineries