With the yeast two hybrid technique, as well as in-vitro and in vivo pull down experiments, the HECT domain of the HERC1 protein was found to bind M2-PK.

Amino-acid sequence of M2-PK

Confocal immunofluorescence microscopy showed a colocalization of both proteins in the perinuclear area.

All results so far appear to indicate that the interaction of HERC1 with M2-PK (PKM2)

• does not induce an ubiquitination and increased degradation of M2-PK.
• does not influence M2-PK enzyme activity or the tetramer : dimer ratio of M2-PK after transient overexpression of HERC1 or its HECT domain in
  HEK-293T cells.

Therefore, the physiological function of the interaction between HERC1 and M2-PK is still not known.

M2-PK not only phosphorylates ADP, but also GDP.

Therefore it might be conceivable that M2-PK functions as a local GTP producer (nano machine) for the RLD1-GEF as well as for the GTPases ARF-1 and Rab5.

HECT

References

The human HERC protein family

M2-PK : a target of different oncogenes