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Insects do not synthesize cholesterol; the 3-hydroxy-3-methylglutaryl-coenzyme-A (HMG-CoA) produced by HMG-CoA synthase is transformed to mevalonate by HMG-CoA reductase for the production of non-sterol isoprenoids, which are essential for growth and differentiation. To understand the regulation and developmental role of HMG-CoA synthase, we have cloned a 1658 bp cDNA that encompasses the entire transcription unit of the HMG-CoA synthase gene from the cockroach Blattella germanica. This cDNA clone was isolated using as a probe a partial cDNA of B. germanica HMG-CoA synthase, amplified using the polymerase chain reaction. Analysis of the nucleotide sequence reveals that the cDNA encodes a polypeptide of 453 amino acids (M(r) 50338) that is similar to vertebrate HMG-CoA synthase (74-76% conserved residues). The B. germanica cDNA has been expressed as a fusion protein in Escherichia coli and exhibits HMG-CoA synthase activity. The HMG-CoA synthase transcript was differentially expressed throughout B. germanica development. Analysis of RNA samples from different adult female tissues shows high HMG-CoA synthase mRNA levels in the ovary and lower levels in brain and muscle. [ABSTRACT FROM AUTHOR]

In insects, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA) synthesizes mevalonate for the production of nonsterol isoprenoids, which are essential for growth and differentiation. To understand the regulation and developmental role of HMG-CoA reductase, we have cloned a full-length HMG-CoA reductase cDNA from the cockroach Blattella germanica. This cDNA clone was isolated using as a probe a partial cDNA of B. germanica HMG-CoA reductase, amplified using the polymerase chain reaction. The composite 3433-bp cDNA sequence contains an open reading frame encoding a polypeptide of 856 amino acids (Mr, 93165). The C-terminal region is more similar to hamster HMG-CoA reductase than is the Drosophila melanogaster enzyme (79% and 69% conserved residues, respectively), and the potential transmembrane domains at the N-terminal region are structurally conservative with both enzymes. The C-terminal region of the B. germanica protein has been expressed as a fusion protein in Escherichia coli and exhibits HMG-CoA reductase activity. Analysis of B. germanica HMG-CoA reductase mRNA levels, reveals a 3.6-kb transcript, that is overexpressed in 4-day-old embryos. Northern-blot analysis of RNA samples from different adult female tissues shows high HMG-CoA reductase mRNA levels in the ovary and lower levels in brain and muscle. [ABSTRACT FROM AUTHOR]