The mycobacterial histidine-rich GroEL1 protein differs
significantly
compared to the well-known methionine/glycine-rich GroEL chaperonin.
It was predicted that mycobacterial GroEL1 can play a significant
role in the metal homeostasis ofMycobacteriabut
not, as its analogue, in protein folding. In this paper, we present
the properties of the GroEL1 His-rich C-terminus as a ligand for Cu(II)
ions. We studied the stoichiometry, stability, and spectroscopic features
of copper complexes of the eight model peptides: L1—Ac-DHDHHHGHAH,
L2—Ac-DKPAKAEDHDHHHGHAH, and six mutants of L2 in the pH range
of 2–11. We revealed the impact of adjacent residues to the
His-rich fragment on the complex stability: the presence of Lys and
Asp residues significantly increases the stability of the system.
The impact of His mutations was also examined: surprisingly, the exchange
of each single His to the Gln residue did not disrupt the ability
of the ligand to provide three binding sites for Cu(II) ions. Despite
the most possible preference of the Cu(II) ion for the His9–His13
residues (Ac-DKPAKAEDHDHHH-) of the model
peptide, especially the His11 residue, the study shows that there
is not only one possible binding mode for Cu(II). The significance
of this phenomenon is very important for the GroEL1 function—if
the single mutation occurs naturally, the protein would be still able
to interact with the metal ion.