STRUCTURAL CHARACTERIZATION OF BA41, A TPM SUPERFAMILY MEMBER FROM THE ANTARCTIC Bizionia argentinensis

CERUTTI ML, OTERO LH, KLINKE S, SMAL C, PELLIZA L, CICERO DO, GOLDBAUM FA, ARAN M

Rosario

Congreso; XLX SAIB ANNUAL MEETING; 2014

SAIB

Bizionia argentinensis (Ba) is a recently annotated Antarctic psychrophilic flavobacterium. Pursuing a comprehensive structural coverage and accurate functional annotation of the Ba genome, a rigorous bioinformatic protocol was applied and several ORFs have been cloned and expressed. BA41 is a hypothetical protein composed by a predicted transmembrane region, a compact domain belonging to the TPM family and a terminal low complexity region. The central TPM domain (BA41s) was cloned, expressed and purified. SLS and DLS studies showed it behaves as a globular monomer of 16 kDa, as expected for a properly folded 150-residue polypeptide. Far-UV CD spectra indicated a high predominance of β-strand secondary structure. Thermal unfolding experiments demonstrated that BA41s is irreversibly denatured and the treatment with EDTA reduces its thermostability by 6°C. The BA41s crystal structure was determined at 1.7 Å resolution by molecular replacement. BA41s displays a Rossmann fold similar to an acid phosphatase from A. thaliana and other two TPM domains belonging to uncharacterized prokaryotic proteins. In accordance with CD experiments, the crystal structure revealed a Zn2+ ion selectively stabilizing the active site folding. Further structural and biochemical studies would help elucidate the functional properties of this protein.