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Biology/Questions

Sequence similarity cannot reveal all functional identity?

by 임은천 2015. 2. 3.

출처: proteinstructures.com


Since large variations in the sequence may result in the same structure, we say that the structure has a higher degree of conservation than the sequence. This is reflected in the fact that the determination of the protein 3D structure may often help revealing its function. An interesting example was provided by the anaerobic cobaltochelatase, an enzyme active in vitamin B12 synthesis. Although the function of the protein was known before structure determination (Schubert et al., 1999), the similarity of the structure to that of ferrochelatase (Al-Karadaghi et al., 1997), an enzyme active in heme biosynthesis, could only be revealed after the structure determination of cobaltochelatase. The reason is that there is only 11% sequence identity between the two proteins, a number much smaller than the so-called "homology-threshold", normally considered in sequence alignment as an indication of evolutionary relationship (around 20-25%).

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