RPSBLAST alignment for GI: 254781111 and conserved domain: cd00385

>gnl|CDD|173830 cd00385, Isoprenoid_Biosyn_C1, Isoprenoid Biosynthesis enzymes, Class 1. Superfamily of trans-isoprenyl diphosphate synthases (IPPS) and class I terpene cyclases which either synthesis geranyl/farnesyl diphosphates (GPP/FPP) or longer chained products from isoprene precursors, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), or use geranyl (C10)-, farnesyl (C15)-, or geranylgeranyl (C20)-diphosphate as substrate. These enzymes produce a myriad of precursors for such end products as steroids, cholesterol, sesquiterpenes, heme, carotenoids, retinoids, and diterpenes; and are widely distributed among archaea, bacteria, and eukaryota.The enzymes in this superfamily share the same 'isoprenoid synthase fold' and include several subgroups. The head-to-tail (HT) IPPS catalyze the successive 1'-4 condensation of the 5-carbon IPP to the growing isoprene chain to form linear, all-trans, C10-, C15-, C20- C25-, C30-, C35-, C40-, C45-, or C50-isoprenoid diphosphates. Cyclic monoterpenes, diterpenes, and sesquiterpenes, are formed from their respective linear isoprenoid diphosphates by class I terpene cyclases. The head-to-head (HH) IPPS catalyze the successive 1'-1 condensation of 2 farnesyl or 2 geranylgeranyl isoprenoid diphosphates. Cyclization of these 30- and 40-carbon linear forms are catalyzed by class II cyclases. Both the isoprenoid chain elongation reactions and the class I terpene cyclization reactions proceed via electrophilic alkylations in which a new carbon-carbon single bond is generated through interaction between a highly reactive electron-deficient allylic carbocation and an electron-rich carbon-carbon double bond. The catalytic site consists of a large central cavity formed by mostly antiparallel alpha helices with two aspartate-rich regions located on opposite walls. These residues mediate binding of prenyl phosphates via bridging Mg2+ ions, inducing proposed conformational changes that close the active site to solvent, stabilizing reactive carbocation intermediates. Generally, the enzymes in this family exhibit an all-trans reaction pathway, an exception, is the cis-trans terpene cyclase, trichodiene synthase. Mechanistically and structurally distinct, class II terpene cyclases and cis-IPPS are not included in this CD. Length = 243
 Score = 95.3 bits (237), Expect = 1e-20
 Identities = 56/168 (33%), Positives = 80/168 (47%), Gaps = 17/168 (10%)

Query: 72  ALRVGAAIECIHCYSLIHDDLPSMDNGYIRRGKPTVHIQ---YDEVTAIIAGNGLLTYAF 128
           A R+ AA+E +H  SL+HDD+  +D+   RRG PT H+         AI+AG+ LL  AF
Sbjct: 12  ASRLRAAVEKLHAASLVHDDI--VDDSGTRRGLPTAHLAVAIDGLPEAILAGDLLLADAF 69

Query: 129 EIISSPKTQLKDNIRSQLMLSLTHNIGLQGMLGGQMLDIQDEF---IDETQVFMIQKMKT 185
           E ++           S   L +     L  +L GQ+LD++          +     + KT
Sbjct: 70  EELA--------REGSPEALEILAEA-LLDLLEGQLLDLKWRREYVPTLEEYLEYCRYKT 120

Query: 186 GALMCFACESGAIMAHASQNEKERLRCFGENLGIIFQLADDLLDCEED 233
             L+   C  GA ++       E LR  G  LG+ FQL +DLLD E D
Sbjct: 121 AGLVGALCLLGAGLSGGEAELLEALRKLGRALGLAFQLTNDLLDYEGD 168