Comparison of a Homology Built Model of Angiogenin to its Crystal Structure

Abstract

The comparison of our homology built model of human angiogenin with the recently determined x-ray structure of the same is reported. The basic details of the structure in terms of alpha -helices and beta sheets were found to be common. The main differences between the model and the x-ray data lie in a C-terminal rearrangement in the x-ray structure that causes the C-terminus to end in a 3₁₀ helix which puts the residue GLN-117 (ALA-122 in bovine pancreatic ribonuclease A, RNaseA) into the active site. The homology model was updated by producing a new sequence alignment using the information from the x-ray data which improved the r.m.s. by 0.5Å. This new alignment is also reported here. A check for systematic bias was carried out using the RNaseA structures from which the x-ray and homology models were derived. A detailed comparison of torsion angles and hydrogen bonding between all the structures have been compared and the model displays several hydrogen bonds that are not present in the parent RNaseA structures but are present in the x-ray structure of angiogenin.