Table 1.

Quantification of the Cu Transfer Efficiency^a

transfer	Cu(I)			Cu(II)
	unbound/bound to donor protein	coelution with acceptor protein	recovery rate	unbound/bound to donor protein	coelution with acceptor protein	recovery rate
PccA → SenC	66%	29%	81%	19%	79%	81%
PccA(ΔM) → SenC	n.a.	n.a.	n.a.	16%	21%	80%
PccA → SenC(ΔC)	90%	10%	96%	88%	12%	83%
SenC → PccA	67%	32%	98%	47%	46%	79%
SenC → PccA(ΔM)	91%	5%	97%	81%	18%	95%

^aQuantification of the Cu transfer reactions from PccA to SenC and from SenC to PccA based on the data shown in Figures 6 and 7. The Cu and protein contents in the individual fractions were determined and calculated in μM. The Cu occupancy was then calculated as (ΣCu_{(W1–W5)[μM)]}/Σprotein_{(W1–W5)[μM]}) × 100% to determine the unbound Cu and the Cu still bound to the donor protein after the transfer reaction (wash fractions). The Cu occupancy of the acceptor protein after the transfer reaction was calculated accordingly as (ΣCu_{(E1–E5)[μM]}/Σprotein_{(E1–E5)[μM]}) × 100% (elution fractions). PccA(ΔM) and SenC(ΔC) refer to protein variants with a mutated Cu binding motif. The Cu recovery rate refers to the total amount of Cu that was recovered in the wash and elution fractions. It was calculated as (ΣCu_{(W1–E5)[μM]}/60 μM) × 100%. It should be noted that the absolute values of the recovery rate for the transfer PccA(ΔM) → SenC are significantly lower than for the other transfer pairs.