Solution structure of a putative ribosome binding protein from Mycoplasma pneumoniae and comparison to a distant homolog.

The solution structure of MPN156, a ribosome-binding factor A (RBFA) protein family member from Mycoplasma pneumoniae, is presented. The structure, solved by nuclear magnetic resonance, has a type II KH fold typical of RNA binding proteins. Despite only approximately 20% sequence identity between MPN156 and another family member from Escherichia coli, the two proteins have high structural similarity. The comparison demonstrates that many of the conserved residues correspond to conserved elements in the structures. Compared to a structure based alignment, standard alignment methods based on sequence alone mispair a majority of amino acids in the two proteins. Implications of these discrepancies for sequence based structural modeling are discussed.