The Assembly Of Mini-MFC And The Crystal Structure Of EIF5-CTD

The assembly of mini-MFC and the crystal structure of eIF5-CTDMultifactor complex (MFC) is an important intermediate in the 43S pre-initiation complex assembly, containing eIFs 1, 2, 3, and 5 and Met-tRNAi^Met. MFC is involved in recruitment of the ternary complex (TC) and recognition of the correct start codon. It plays a critical role in the process of translation initiation. Mini-MFC is the core of MFC, containing eIFl, eIF2β-NTD, eIF3c-NTD and eIF5-CTD. eIF5-CTD can directly interact with eIFl, eIF2β-NTD and eIF3c-NTD, bridging the assembly of the mini-MFC.eIF5, a GTPase-activating protein (GAP) specific for eIF2, plays a critical role in pre-initiation complex assembly and correct AUG selection during eukaryotic translation initiation. eIF5 is involved in the formation of the multifactor complex (MFC), an important intermediate of the 43 S preinitiation complex. The C-terminal domain (CTD) of eIF5 functions as the structural core in the mini-MFC assembly. It also can interact with eIF4G and play an important role in the assembly of 43S complex and 48S complex.In this study, we examined complex formation between eIFl, eIF2β-NTD, eIF3c-NTD and eIF5-CTD by Gel filtration. It provides some important information for the future study on the crystal structure of mini-MFC complex. In addition, We solved the 1.5A crystal structure of eIF5-CTD, confirming that eIF5-CTD contains an atypical HEAT motif. In addition, analyzing the electrostatic potential and the distribution of conserved residues on the protein surface, we confirm and suggest some potential regions of interactions between eIF5-CTD and other eIFs. The structure of eIF5-CTD provides useful information in understanding the mechanism of the MFC assembly.The crystal structure of leptospira cbiCThe leptospira cbiC encodes the enzyme catalyzing the methyl rearrangement reaction of the cobalamin biosynthesis pathway. Cobalamin (vitamin B12) is an evolutionarily ancient cofactor and one of the largest, most structurally complex, nonpolymeric biomolecules described. Vitamin B12 is an essential nutrient for many animals and must be acquired by ingestion. Vitamin B12 (cobalamin) is synthesized by aerobic and anaerobic two alternative pathways. One pathway incorporates molecular oxygen into the macrocycle as a prerequisite to ring contraction, and has consequently been termed the aerobic pathway. The alternative, anaerobic, route takes advantage of a chelated cobalt ion, in the absence of oxygen, to set the stage for ring contraction.The protein has been cloned and overexpressed as a His-tagged recombinant protein in Escherichia coli. The crystal structures have been solved in two crystal forms (P42212 and P3121) diffracting to 3.0 and 2.3A°resolution, respectively. The structures are similar to the precorrin-8x methyl mutase (CobH), an enzyme involved in the aerobic pathway.