Final answer:
Despite low sequence identity, proteins can have similar structures and functions because protein folding is highly conserved evolutionarily, and functional domains can be preserved. Computational tools like BLAST aid in analyzing these similarities.
Step-by-step explanation:
A protein match with only a 30% sequence identity can still be a good model for similar structures primarily because structural similarity can exist even with low sequence identity. This phenomenon occurs because protein folding, which determines the three-dimensional shape, is often conserved across species despite variations in the precise amino acid sequence.
Furthermore, functional similarity may not rely solely on a high sequence identity. In some cases, critical active sites or binding domains are conserved even when other parts of the sequence vary significantly. This allows for the retention of function despite the sequence divergence. The Protein Data Bank (PDB) is indeed a reliable database, and experimental errors, although possible, are generally identified and corrected in the process of sequence alignment and structure determination.
Therefore, the similarity in the protein structure of the two proteins would likely be high based on the conservation of protein folding and function, rather than the low sequence identity. Computational tools such as BLAST can aid in comparing protein sequences and structures to draw conclusions about their evolutionary relationship and functional similarities.