1Z3Y

Structure of Gun4-1 from Thermosynechococcus elongatus

Summary for 1Z3Y

• Entry DOI: 10.2210/pdb1z3y/pdb
• Related: 1Z3X
• Descriptor: putative cytidylyltransferase (2 entities in total)
• Functional Keywords: transferase activator
• Biological source: Thermosynechococcus elongatus
• Total number of polymer chains: 1
• Total formula weight: 27406.08

Authors

Davison, P.A.,Schubert, H.L.,Reid, J.D.,Iorg, C.D.,Robinson, H.,Hill, C.P.,Hunter, C.N. (deposition date: 2005-03-14, release date: 2005-06-07, Last modification date: 2024-04-03)

Primary citation

Davison, P.A.,Schubert, H.L.,Reid, J.D.,Iorg, C.D.,Heroux, A.,Hill, C.P.,Hunter, C.N.
Structural and Biochemical Characterization of Gun4 Suggests a Mechanism for Its Role in Chlorophyll Biosynthesis(,).
Biochemistry, 44:7603-7612, 2005

PubMed Abstract: Gun4 has been implicated in a developmental signaling pathway between the chloroplast and the nucleus involving magnesium protoporphyrin IX (MgP(IX)), the first dedicated intermediate in the chlorophyll biosynthetic pathway. Here we present the crystal structure of Thermosynechococcus elongatus Gun4 at 1.5 A, describe the binding affinities of Gun4 for substrate and product porphyrin molecules, and identify a likely (Mg)P(IX) binding site on the protein. Kinetic analyses show that Gun4 dramatically increases the efficiency of transformation of porphyrin substrate to metalloporphyrin product and that it also reduces the threshold Mg2+ concentration required for activity at low porphyrin concentration. Gun4 therefore controls magnesium chelatase at physiologically significant Mg2+ concentrations and likely acts as a molecular switch in vivo so that in its absence magnesium chelatase is inactive. This mechanism could allow Gun4 to mediate magnesium protoporphyrin levels both for chlorophyll biosynthesis and for signaling to the nucleus.

PubMed: 15909975
DOI: 10.1021/bi050240x

Experimental method

X-RAY DIFFRACTION (1.7 Å)