3‐Hydroxy‐3‐methylglutaryl‐coenzyme‐A synthase from Blattella germanica

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Abstract
Insects do not synthezise 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 (Mr 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.