Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Moraxella lacunata is a bacterium that is a causative agent of human conjunctivitis and keratitis. We have previously cloned the Q and I pilin (formerly called beta and alpha pilin) genes of Moraxella bovis and determined that an inversion of 2 kilobases (kb) of DNA determines which pilin gene is expressed. Using an M. bovis pilin gene as a hybridization probe to screen a lambda ZAP library of M. lacunata DNA, we have isolated a clone that not only contains the entire type 4 pilin gene inversion region of M. lacunata but inverts the 2-kb region on a plasmid subclone (pMxL1) in Escherichia coli. Deletion derivatives of pMxL1 yielded some plasmids that still had the entire inversion region but were phase locked into one or the other of the two potential orientations. Similarly, insertions of a 2-kb streptomycin-resistant element (omega) within some regions outside of the inversion also resulted in phase-locked plasmids. These deletions and insertions thus localize a probable invertase necessary for the inversion event. The region was sequenced, and an open reading frame with over 98% DNA sequence homology to an open reading frame that we previously found in M. bovis and called ORF2 appeared to be a strong candidate for the invertase. This conclusion was confirmed when a plasmid containing the M. bovis ORF2 supplied, in trans, the inversion function missing from one of the M. lacunata phase-locked inversion mutants. We have named these putative invertase genes piv(ml) (pilin inversion of M. lacunata) and piv(mb) (pilin inversion of M. bovis). Despite previously noted sequence similarities between the M. bovis sites of inversion and those of the Hin family of invertible segments and a 60-base-pair region within the inversion with 50% sequence similarity to the cin recombinational enhancer, there is no significant sequence similarity of the Piv invertases to the Hin family of invertases.
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PMID:Identification, cloning, and sequencing of piv, a new gene involved in inverting the pilin genes of Moraxella lacunata. 197 27

To study the regulation of fructan synthesis in plants, we isolated two full-size cDNA clones encoding the two enzymes responsible for fructan biosynthesis in Jerusalem artichoke (Helianthus tuberosus): 1-sucrose:sucrose fructosyl transferase (1-SST) and 1-fructan:fructan fructosyl transferase (1-FFT). Both enzymes have recently been purified to homogeneity from Jerusalem artichoke tubers (Koops and Jonker (1994) J.Exp.Bot.45, 1623-1631; Koops and Jonker (1996) Plant Physiol. 110, 1167-1175) and their amino acid sequences have been partially determined. Using RT-PCR and primers based on these sequences, specific fragments of the genes were amplified from tubers of Jerusalem artichoke. These fragments were used as probes to isolate the cDNAs encoding 1-SST and 1-FFT from a tuber-specific lambdal ZAP library. The deduced amino acid sequences of both cDNAs perfectly matched the sequences of the corresponding purified proteins. At the amino acid level, the cDNA sequences showed 61% homology to each other and 59% homology to tomato vacuolar invertase. Based on characteristics of the deduced amino acid sequence, the first 150 bp of both genes encode a putative vacuolar targeting signal. Southern blot hybridization revealed that both 1-SST and 1-FFT are likely to be encoded by single-copy genes. Expression studies based on RNA blot analysis showed organ-specific and developmental expression of both genes in growing tubers. Lower expression was detected in flowers and in stem. In other organs, including leaf, roots and dormant tubers, no expression could be detected. In tubers, the spatial and developmental expression correlates with the accumulation of fructans. Using the 1-sst and 1-fft cDNAs, chimeric genes were constructed driven by the CaMV 35S promoter. Analysis of transgenic petunia plants carrying these constructs showed that both cDNAs encode functional fructosyltransferase enzymes. Plants transformed with the 35S-1-sst construct accumulated the oligofructans 1-kestose (GF2), 1,1-nystose (GF3) and 1,1,1-fructosylnystose (GF4). Plants transformed with the 35S-1-fft construct did not accumulate fructans, probably because of the absence of suitable substrates for 1-FFT, i.e. fructans with a degree of polymerization > or = 3 (GF2, GF3, etc.). Nevertheless, protein extracts from these transgenic plants were able to convert GF3, when added as a substrate into fructans with a higher degree of polymerization. Progeny of crosses between a 35S-1-sst-containing plant and a 35S-1-fft-containing plant, showed accumulation of high-molecular-weight fructans in old, senescent leaves. Based on the comparison of the predicted amino acid sequences of 1-sst and 1-fft with those of other plant fructosyl transferase genes, we postulate that both plant fructan genes have evolved from plant invertase genes.
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PMID:Cloning of the fructan biosynthesis pathway of Jerusalem artichoke. 975 74