Structural and functional conservation between yeast and human 3-hydroxy-3-methylglutaryl coenzyme A reductases, the rate-limiting enzyme of sterol biosynthesis.

Abstract

The pathway of sterol biosynthesis is highly conserved in all eucaryotic cells. We demonstrated structural and functional conservation of the rate-limiting enzyme of the mammalian pathway, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) Analysis of sterol biosynthesis in the yeast Saccharomyces cerevisiae and in mammalian cells (7) led to the biochemical elucidation of this pathway, which produces all isoprene-containing compounds, including sterol, ubiquinone, dolichol, and isopentenylated adenosine in tRNA. The enzymatic steps of this pathway are highly conserved between S. cerevisiae and larger eucaryotes. Although the regulation of this pathway in yeast cells remains virtually unexplored, it has been examined extensively in mammalian cells. These studies have revealed that 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) is the rate-limiting enzyme of the mammalian pathway.The rates of synthesis and degradation of mammalian HMG-CoA reductase are controlled by negative feedback regulation. Serum cholesterol in the form of low-density lipoprotein reduces the steady-state level of HMG-CoA reductase mRNA (14, 32) and also decreases the half-life of the protein (11,18). An unidentified nonsterol product of the pathway provides additional negative feedback regulation (9, 44). The response of HMG-CoA reductase to the diurnal cycle and to several hormones may be mediated by reversible phosphorylation of the enzyme (6, 55) and by allosteric effectors (49).Mammalian HMG-CoA reductase is an integral membrane glycoprotein of the endoplasmic reticulum (8, 34) and has also been identified in peroxisomes (29). A structural model for the endoplasmic reticulum form of hamster HMG-CoA reductase has been proposed which is based on secondarystructure predictions from the primary sequence and on proteolysis experiments (33). The NH2-terminal one-third of the protein (amino acids 1 to 339) is membrane bound and contains seven potential membrane-spanning domains and a single N-linked

The Role of the 3-Hydroxy 3-Methylglutaryl Coenzyme A Reductase Cytosolic Domain in Karmellae Biogenesis

“…Although details concerning the structure and function of the HMG-CoA reductase catalytic domain are beginning to be solved (Darnay et al, 1992;Lawrence et al, 1995;Rogers et al, 1997;Tabernero et al, 1999), the HMG-CoA reductase membrane domain remains much more cryptic. In plants, the membrane domain contains two transmembrane helices (Denbow et al, 1996;Re et al, 1997), whereas in animals and fungi, it contains of a series of seven or eight transmembrane helices (Liscum et al, 1985;Basson et al, 1988;Sengstag et al, 1990;Olender and Simon, 1992;Roitelman et al, 1992). Although there is little obvious primary sequence conservation, the structural conservation of this complex membrane domain over the 1 billion years of evolution since divergence of fungi and animals (Doolittle et al, 1996;Lum et al, 1996;Feng et al, 1997) suggests that the structure has an important functional role.…”

Isolation and Characterization of cDNAs Encoding Wheat 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase

“…The first section at the base of the leaf is the youngest, and the tip section is the oldest (Fig. 8) (Caelles et al, 1989;Learned and Fink, 1989), tomato (Narita and Gruissem, 1989), human (Luskey and Stevens, 1985), yeast (Basson et al, 1988), and Drosophila (Gertler et al, 1988). Relative to the wheat sequence, identical or conserved residues are shown in gray and residues that are neither identical nor conserved are shown in white.…”

“…The degree of sequence homology among the three cDNAs is very high, as indicated by the shading. Figure 3 shows sequence homology comparison among HMGR genes by computer alignment of the translated wheat HMGR 18 partial cDNA sequence with that from Arabidopsis (Caelles et al, 1989;Learned and Fink, 1989), tomato (Narita and Gruissem, 1989;Narita et al, 1991), human (Luskey and Stevens, 1985), yeast (Basson et al, 1988), and Drosophila (Gertler et al, 1988).…”

“…cDNAs and genomic HMGR clones have been isolated from Drosophila (Gertler et al, 1988), yeast (Basson et al, 1988), sea urchin (Woodward et al, 1988), hamster (Chin et al, 1984), and human (Luskey and Stevens, 1985). Recently, with the use of hamster and yeast probes plant HMGR cDNAs and genomic clones have been isolated from Arabidopsis (Caelles et al, 1989;Leamed and Fink, 1989), tomato (Narita and Gruissem, 1989;Narita et al, 1991), and Hevea (Chye et al, 1991).…”

Sequence comparison of a segment of the gene for 3‐hydroxy‐3‐methylglutaryl‐coenzyme A reductase in zygomycetes

“…* * * * * * * * * * ** t t * * * * * * * * * * * [19], Gibberella fujikuroi (Gj) [20], Phycomyces blakesleeanus (Pb) [20], Absidia glauca (Ag), Blakeslea trispora (Bt), Mucor mucedo (Mm) and Parasitella parasitica (PP).…”