Why doesn my protein begin with methionine?
Question: “I am looking at KIAA1247 on chr 20q13, which according to the UCSC genome browser details page begins its amino acid sequence as DSRIPKEAPDQQKKKMGPPSLVLCLLS, and also at KIAA1077 on chr 8q13.3 that begins DVELGSLQVMNKTRKIMEHG. Can I trust your data? I thought nuclear-encoded human proteins always began with methionine?” Response: The UCSC genome browser uses translated mRNA data exactly as supplied to GenBank by the original sequencing authors. Any errors at GenBank propagate through many other databases and tools. To work effectively in a bioinformatic area subject to errors, it is a good idea to seek supporting data for any unusual finding. In the case of KIAA1247, by using BLAT or BLAST to recover other close members of this human gene family (GNS, SGSH, ARSA, ARSB, GALNS, ARSE, ARSD, STS, and IDS), we learn from comparative alignment that the 5’UTR in mRNA for KIAA1247 was likely misintepreted as coding sequence and that the protein begins with methionine as expected: ds
