1H and 15N NMR assignments of PsaE, a photosystem I subunit from the cyanobacterium Synechococcus sp. strain PCC 7002.
PsaE is a highly conserved, water-soluble protein of the photosystem I reaction center complexes of cyanobacteria, algae, and green plants. Along with the PsaC and PsaD proteins, the PsaE protein binds to the stromal surface of photosystem I and is required for cyclic electron transport in Synechococcus sp. strain PCC 7002 [Yu, L., Zhao, J., Mühlenhoff, U., Bryant, D.A., & Golbeck, J.H. (1993) Plant Physiol. 103, 171-180]. The psaE gene from this cyanobacterium encodes a mature protein of 69 amino acid residues and has recently been overexpressed in Escherichia coli [Zhao, J., Snyder, W.B., Mühlenhoff, U., Rhiel, E., Warren, P. V., Golbeck, J. H., & Bryant, D. A. (1993) Mol. Microbiol. 9, 183-194]. By using both unlabeled and uniformly 15N-labeled protein in a series of two- and three-dimensional NMR experiments, complete 1H and 15N amide resonance assignments were made. The major secondary structural element of PsaE is a five-stranded antiparallel beta-sheet. The five strands extend as follows: beta A, residues 7-10; beta B, residues 21-26; beta C, residues 36-39; beta D, residues 57-60; and beta E, residues 65-68. The topology is represented by (+1, +1, +1, -4x); it brings the first and last strands, and consequently the N- and C-termini, together. The protein has an extensive hydrophobic core organized around a conserved phenylalanine residue (Phe-40); another of its distinctive features is a segment extending from residue 42 to residue 56 devoid of dipolar contacts with the beta-sheet. The pK1/2 of the sole histidine residue (His-63) was determined to be 5.4.
Falzone
C J
CJ
Department of Chemistry, Pennsylvania State University, University Park 16802.
Kao
Y H
YH
Zhao
J
J
MacLaughlin
K L
KL
Bryant
D A
DA
Lecomte
J T
JT
D000595:Amino Acid Sequence; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D000458:Cyanobacteria / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010649:Phenylalanine / Q000737:chemistry; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D045331:Photosystem I Protein Complex; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
D046911:Macromolecular Substances; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D011994:Recombinant Proteins; C079741:photosystem I, psaE subunit; D010649:Phenylalanine