An unexpected phosphate binding site in Glyceraldehyde 3-Phosphate Dehydrogenase: Crystal structures of apo, holo and ternary complex of Cryptosporidium parvum enzyme

Table 2 GAPDH complexes with substrate or substrate analogue.

PDB number	Reference	NAD present	Substrate	No. of subunits with substrate	Ps or New Pi* site	Soaked or Co-crystallized
CpGAPDH	This structure	Yes	D-glyceraldehyde 3-phosphate	4	New Pi^&	Co-crystal
1GYP	17	Yes	PO₄	4	Ps and new Pi	Co-crystal
1DC4	16	No	D-glyceraldehyde 3-phosphate	2^#	New Pi	Soaked
1NQO	15	Yes	D-glyceraldehyde 3-phosphate	4	Ps	Soaked
3CMC	12	Yes	D-glyceraldehyde 3-phosphate	4	New Pi	Soaked
1ML3	14	Yes	(3-formyl-but-3-enyl)-phosphonic acid	3⁺	Ps	Co-crystal
1QXS	18	Yes	1,3-biphospho-D-glyceric acid	1^$	Ps	Co-crystal

* The 'new Pi' site is defined as the site of the phosphate in 1GYP, which contains only phosphate and NAD.
^&Only subunits A, B and C. The D-G3H molecule in subunit D occupies a different position that does not correspond to any previously reported phosphate position.
^# Two subunits per asymmetric unit.
⁺ Two conformers in the structure. Subunit D has only conformer A, and its phosphate moiety binds in the 'Ps' site. Subunits B and C have both conformers at 50% occupancy; the phosphate moiety in conformer B binds in a site that is 2.5 to 2.8 Å from the 'new Pi' site.
^$ Only one subunit (subunit C) binds the analogue. One of the phosphate moieties binds in the 'Ps' site. The other binds in a site that is 2.8 Å from the 'new Pi' site.

ISSN: 1472-6807