Table 3.

Helix 2 Dipole Moments for hGrx1 and hGrx2^a

Grx structure	dipole moment (D)	helix–thiolate angle (deg)	component of dipole (D)
hGrx1 (1)	182	24.4	166
hGrx1 (6)	170	19.7	160
hGrx1 (16)	177	19.2	167
hGrx1 (20)	168	24.4	153
hGrx2	213	10.6	209

^aPartial PDB files of hGrx1 [1JHB (23)] and hGrx2 [2FLS (39)] were submitted to the Protein Dipole Moments Server [http://bioportal.weizmann.ac.il/dipol/ (40)] to calculate the dipole moment of helix 2, as well as the angle between the helix and catalytic cysteine (see Experimental Procedures). For hGrx1, the number in parentheses indicates the specific NMR structure shown previously to predict the empirically observed catalytic cysteine pK_a of approximately 3.5 (30). The component of each dipole directed toward the catalytic cysteine was calculated by multiplying the dipole moment by the cosine of the angle formed by the intersection of the helix axis with a line projecting from the base of the helix to the catalytic cysteine.