A human sperm is about 60 micrometers long and has a head, neck, mid piece and tail. The head contains the acrosome (containing enzymes) and nucleus while the middle piece containing mitochondria supplies energy to allow the sperm to swim to fertilize the egg.
Mitochondria are considered the power plant of a cell as they provide ATP that is needed for many metabolic processes in the cell. They produce ATP through a complex metabolic pathway called oxidative phosphorylation, or OXPHOS.
The mitochondria are a central part of the highly streamlined sperm structure which makes them specialized for finding and fusing with an egg. Although the organelles are essential to sperm function they are often poorly understood.
We have recently shown that the midpiece of amniote sperm has extensive arrays of organized mitochondria, which are physically coupled to the axoneme via microtubule doublets. This arrangement is important for axoneme bending, enabling the sperm to slide past the flagellum and into the uterus.
However, the precise molecular mechanisms by which these arrays tether to the underlying cytoskeleton are still unclear. This knowledge could be useful in other specialized and polarized cell types where organelles are anchored to their underlying cytoskeleton.
It has been reported that a peptide fusion protein, phospholipid hydroperoxide glutathione peroxidase (PHGPx), is necessary for the formation of the'mitochondrial sheath'. This sheath is a crescent shape that is formed by intermolecular disulfide bonds between cysteine and proline-rich proteins.
