1H and 15N NMR Assignments of PsaE, a Photosystem I Subunit from the Cyanobacterium Synechococcus sp. Strain PCC 7002

Christopher J. Falzone, Yung Hsiang Kao, Kristen L. MacLaughlin, Juliette T.J. Lecomte, Jindong Zhao, Donald A. Bryant

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Abstract

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., Muhlenhoff, 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 β-sheet. The five strands extend as follows: βA, residues 7–10; βB, residues 21–26; βC, residues 36–39; βD, residues 57–60; and βE, 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 β-sheet. The pK1/2 of the sole histidine residue (His-63) was determined to be 5.4.

Original languageEnglish (US)
Pages (from-to)6043-6051
Number of pages9
JournalBiochemistry
Volume33
Issue number20
DOIs
StatePublished - May 1 1994

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All Science Journal Classification (ASJC) codes

  • Biochemistry

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