Chains and heterogens:
PDB Chain Sequences:
>1sm4A (A:) iskkqdegvvvnkfrpkepyigrcllntkitgddapgetwhmvfstegeipyregqsigv iadgvdangkphklrlysiassalgdfgdsktvslcvkrlvytndkgeevkgvcsnflcd lkpgadvkitgpvgkemlmpkdpnatvimlgtgtgiapfrsflwkmffekhddykfngla wlflgvptsssllykeefekmkekapenfrldfavsreqtnekgekmyiqtrmaqyaeel wtllkkdntfvymcglkgmeqgiddimsslaakegidwadykkqlkkaeqwnvevy
>1sm4B (B:) iskkqdegvvvnkfrpkepyigrcllntkitgddapgetwhmvfstegeipyregqsigv iadgvdangkphklrlysiassalgdfgdsktvslcvkrlvytndkgeevkgvcsnflcd lkpgadvkitgpvgkemlmpkdpnatvimlgtgtgiapfrsflwkmffekhddykfngla wlflgvptsssllykeefekmkekapenfrldfavsreqtnekgekmyiqtrmaqyaeel wtllkkdntfvymcglkgmeqgiddimsslaakegidwadykkqlkkaeqwnvevy