Characterization of the full-length btuB riboswitch from Klebsiella pneumoniae.

Riboswitches are cis-regulatory RNA elements on the mRNA level that control the expression of the downstream coding region. The interaction of the riboswitch with its specific metabolite, which is related to the function of the controlled gene, induces a structural change of the RNA architecture. Consequently, gene regulation is induced by un/masking of the ribosome binding site (RBS). In the genome of Klebsiella pneumoniae a sequence was identified by bioinformatics and proposed to be a B12 riboswitch regulated by coenzyme B12. Here we study this new coenzyme B12-dependent riboswitch system by in-line probing and ITC. The riboswitch sequence includes the whole expression platform as well as RBS. In-line probing experiments were performed to investigate the structural rearrangement of this 243-nt long RNA sequence while Isothermal Titration Calorimetry (ITC) yielded the thermodynamic parameters of the interaction between the riboswitch and its metabolite. The interaction of coenzyme B12 with the butB riboswitch of K. pneumoniae is an exothermic process with a 1:1 binding stoichiometry and binding affinities of log KA=6.73±0.02 at 15°C and log KA=6.00±0.09 at 30°C.

[Findings in relation to serum and urinary iron in heterozygotic beta-thalassemia]. / Indagine intorno al ferro sierico ed urinario nella beta-talassemia eterozigote.

Iron status (expressed as serum ferritin and iron levels) has been compared in normal and in heterozygous beta-thalassemic subjects. A higher serum ferritin concentration has been found in beta-thalassemic males, showing, therefore, a shift towards super-normal values of the balance between tissue iron and serum ferritin levels. In beta-thalassemic subjects the serum ferritin levels have been found in the normal range and this seems to be correlated with an adequate and ready iron supply by protein transferrin to hyperplastic bone marrow. The higher urinary iron values in normal male subjects can be explained in this way: a large iron supply from the transferrin to the thalassemic erythroid cells limits the contribution from this protein to the urinary iron.