Chains and heterogens:
PDB Chain Sequences:
>1bt4A (A:) seraynfnagpaalplevleraqaefvdyqhtgmsimemshrgavyeavhneaqarllal lgnptgykvlfiqggastqfamipmnflkegqtanyvmtgswaskalkeakligdthvaa sseasnymtlpklqeiqlqdnaaylhltsnetiegaqfkafpdtgsvpligdmssdilsr pfdlnqfglvyagaqknlgpsgvtvvivredlvaespkhlptmlrydtyvknnslyntpp sfgiymvnevlkwieergglegvqqanrkkasliydaidqsggfyrgcvdvdsrsdmnit frlaseelekefvkaseqegfvglkghrsvgglrasiynavpyescealvqfmehfkrsr g