Chains and heterogens:
PDB Chain Sequences:
>1ursA (A:) cgtsnggqntspstssssakgeasalpkgqtitvwswqtgpelqdvkqiaaqwakahgdk vivvdqssnpkgfqfyataartgkgpdvvfgmphdnngvfaeeglmapvpsgvlntglya pntidaikvngtmysvpvsvqvaaiyynkklvpqppqtwaefvkdanahgfmydqanlyf dyaiiggyggyvfkdnngtldpnnigldtpgavqaytlmrdmvskyhwmtpstngsiaka eflagkigmyvsgpwdtadiekakidfgvtpwptlpngkhatpflgvitafvnkesktqa adwslvqaltsaqaqqmyfrdsqqipallsvqrssavqssptfkafveqlryavpmpnip qmqavwqamsilqniiagkvspeqgakdfvqniqkgimaqgs
>1ursA (A:) qtitvwswqtgpelqdvkqiaaqwakahgdkvivvdqssnpkgfqfyataartgkgpdvv fgmphdnngvfaeeglmapvpsgvlntglyapntidaikvngtmysvpvsvqvaaiyynk klvpqppqtwaefvkdanahgfmydqanlyfdyaiiggyggyvfkdnngtldpnnigldt pgavqaytlmrdmvskyhwmtpstngsiakaeflagkigmyvsgpwdtadiekakidfgv tpwptlpngkhatpflgvitafvnkesktqaadwslvqaltsaqaqqmyfrdsqqipall svqrssavqssptfkafveqlryavpmpnipqmqavwqamsilqniiagkvspeqgakdf vqniqkg
>1ursB (B:) cgtsnggqntspstssssakgeasalpkgqtitvwswqtgpelqdvkqiaaqwakahgdk vivvdqssnpkgfqfyataartgkgpdvvfgmphdnngvfaeeglmapvpsgvlntglya pntidaikvngtmysvpvsvqvaaiyynkklvpqppqtwaefvkdanahgfmydqanlyf dyaiiggyggyvfkdnngtldpnnigldtpgavqaytlmrdmvskyhwmtpstngsiaka eflagkigmyvsgpwdtadiekakidfgvtpwptlpngkhatpflgvitafvnkesktqa adwslvqaltsaqaqqmyfrdsqqipallsvqrssavqssptfkafveqlryavpmpnip qmqavwqamsilqniiagkvspeqgakdfvqniqkgimaqgs
>1ursB (B:) titvwswqtgpelqdvkqiaaqwakahgdkvivvdqssnpkgfqfyataartgkgpdvvf gmphdnngvfaeeglmapvpsgvlntglyapntidaikvngtmysvpvsvqvaaiyynkk lvpqppqtwaefvkdanahgfmydqanlyfdyaiiggyggyvfkdnngtldpnnigldtp gavqaytlmrdmvskyhwmtpstngsiakaeflagkigmyvsgpwdtadiekakidfgvt pwptlpngkhatpflgvitafvnkesktqaadwslvqaltsaqaqqmyfrdsqqipalls vqrssavqssptfkafveqlryavpmpnipqmqavwqamsilqniiagkvspeqgakdfv qniqkg