Sequencing of cDNA and proximal promoter of equine hexokinase II gene.

This study aims to understand how horses utilize glucose by analysing the coding and promoter sequences of the equine hexokinase type II (HKII) gene in different breeds of horse and zebra. The findings reveal several unique substitutions within the glucose-binding site of the equine HKII, along with multiple potential binding sites for the transcription factor in the proximal promoter region of the gene.

Investigating Glucose Utilisation in Horses

• The researchers set out to understand how glucose is utilised in equine skeletal muscle. This metabolic process is important for basic cellular function and energy production.
• To do this, they examined an enzyme known as hexokinase type II (HKII) which plays a critical role in the initial steps of glucose metabolism.
• The HKII gene was analysed in thoroughbred horse, Grevy’s zebra and Hartmann’s mountain zebra to have a broader perspective of different equine species.

Sequence Analysis of Equine HKII

• The researchers focused on two main parts of the HKII gene: the coding sequence, which contains the instructions for making the enzyme; and the proximal promoter sequence, a region that controls when and where the gene is switched on.
• The coding sequence of the thoroughbred horse HKII showed high identity with Grevy’s zebra, Hartmann’s mountain zebra, human, mouse and rat HKII sequences. This indicates that the gene is highly conserved across these species, suggesting a common function.
• In addition, two specific amino acid substitutions – Ile 159 and Arg 610 – were identified in the potential glucose binding site of the equine HKII gene. These substitutions may change the way the enzyme interacts with glucose.

Proximal Promoter Analysis of Equine HKII

• The proximal promoter sequence controls the initiation of gene transcription, acting as a binding site for various transcription factors.
• The researchers identified numerous conserved putative binding sites for transcription factors within the equine HKII gene’s proximal promoter.
• This discovery suggests that the regulation of the HKII gene, and therefore glucose usage within equine skeletal muscle, may be under complex control by various transcription factors.