. Author manuscript; available in PMC: 2010 Jul 1.

Published in final edited form as: Chem Rev. 2009 Jul;109(7):2903–2928. doi: 10.1021/cr900021w

Table 3. Monovalent cation selectivity in IMPDH.

All IMPDHs are activated by K⁺, NH₄⁺ and Rb⁺, but the effects of Na⁺ vary among IMPDHs from different organisms. The sequences of the Cys319 loop (residues 312-331) and C-terminal helix (residues 480-487) are shown; residues that interact with K⁺ are shown in bold. The % helix is calculated for the corresponding peptide using AGADIR ²⁷⁴. conditions: ionic strength = 0.1, 278 degrees K, pH 7. a. ⁸⁴; b. ¹⁴⁷; c. ¹⁴³

Source	Na⁺	Cys 319 loop	C-term helix	%helix
C. parvum	no effect	GIGPGSICTTRIVAGVGVPQ	TTSGLRESH	0.54
B. burgdorferi^a	inhibits	GIGPGSICTTRIVAGVGVPQ	SHSSLKESH	0.40
S. pyogenes	unknown	GIGPGSICTTRVVAGVGVPQ	SGAGLIESH	0.24
E. coli^b	inhibits	GIGPGSICTTRIVTGVGVPQ	SGAGIQESH	0.30
human type 2^c	activates	GNGSGSICITQEVLACGRPQ	TSSAQVEGG	0.27
T. foetus	activates	GIGGGSICITREQKGIGRGQ	SSVSIVEGG	0.16