MYPFFTYSPGRHYFEYKWYNLELLRLIGSAPYGGCDAAEFLELVASLKPN
DADEWHHKFLALAERTQAKGEQMSEAGHEAVARGAYLRASNYFRCAQYMF
PIMPAARQGEFLKLYHRSIRSFEQAAELMEHRVERVSIPFQPPEYRAPAV
ELPGWLHLPAAHQRLSGRKTPLLICVGGADSTQEELYFLSAAEGPGLGYA
ILTFDGPGQGLTLRESGVPLRPDGEVVIEAVLDFIESYAAEHPEADLDVD
AISITGQSLGGYLALRGAADPRIKACVAVDPIYDFYDLAMSRMPRWFMWP
WERNYMGDGFVDFAVIEHSKLDVATKYTFAQGGQMFGSASPAQMIRDMKQ
YTFRLDKTITASKRHGNNRDYLEWVTCPVFVTGAAGDEKLFLPEMSTSAI
MRNLANVPDEHKELWIPKEWSEGGAQAKSGAWPLLQHRCFKFLDEKLGIS
R
LegendThis sequence has been compared to family alignement (MSA) red => minority aminoacid blue => majority aminoacid color intensity => conservation rate title => sequence position(MSA position)aminoacid rate Catalytic site Catalytic site in the MSA MYPFFTYSPGRHYFEYKWYNLELLRLIGSAPYGGCDAAEFLELVASLKPN DADEWHHKFLALAERTQAKGEQMSEAGHEAVARGAYLRASNYFRCAQYMF PIMPAARQGEFLKLYHRSIRSFEQAAELMEHRVERVSIPFQPPEYRAPAV ELPGWLHLPAAHQRLSGRKTPLLICVGGADSTQEELYFLSAAEGPGLGYA ILTFDGPGQGLTLRESGVPLRPDGEVVIEAVLDFIESYAAEHPEADLDVD AISITGQSLGGYLALRGAADPRIKACVAVDPIYDFYDLAMSRMPRWFMWP WERNYMGDGFVDFAVIEHSKLDVATKYTFAQGGQMFGSASPAQMIRDMKQ YTFRLDKTITASKRHGNNRDYLEWVTCPVFVTGAAGDEKLFLPEMSTSAI MRNLANVPDEHKELWIPKEWSEGGAQAKSGAWPLLQHRCFKFLDEKLGIS R
UCS1025A is a fungal polyketide/alkaloid that displays strong inhibition of telomerase. The structures of UCS1025A and related natural products are featured by a tricyclic furopyrrolizidine connected to a trans-decalin fragment. We mined the genome of a thermophilic fungus and activated the ucs gene cluster to produce UCS1025A at a high titer. Genetic and biochemical analysis revealed a PKS-NRPS assembly line that activates 2S,3S-methylproline derived from l-isoleucine, followed by Knoevenagel condensation to construct the pyrrolizidine moiety. Oxidation of the 3S-methyl group to a carboxylate leads to an oxa-Michael cyclization and furnishes the furopyrrolizidine. Our work reveals a new strategy used by nature to construct heterocyclic alkaloid-like ring systems using assembly line logic.
