Journal Article

Positive Charges on Lysine Residues of the Extrinsic 18 kDa Protein Are Important to Its Electrostatic Interaction with Spinach Photosystem II Membranes

Jin-Peng Gao, Zhen-Hua Yong, Feng Zhang, Kang-Cheng Ruan, Chun-He Xu and Gen-Yun Chen

Edited by Li-Xin Zhang

in Acta Biochimica et Biophysica Sinica

Published on behalf of Institute of Biochemistry and Cell Biology, SIBS, CAS

Volume 37, issue 11, pages 737-742
Published in print November 2005 | ISSN: 1672-9145
Published online November 2005 | e-ISSN: 1745-7270 | DOI: https://dx.doi.org/10.1111/j.1745-7270.2005.00103.x
Positive Charges on Lysine Residues of the Extrinsic 18 kDa Protein Are Important to Its Electrostatic Interaction with Spinach Photosystem II Membranes

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To determine the contribution of charged amino acids to binding with the photosystem II complex (PSII), the amino or carboxyl groups of the extrinsic 18 kDa protein were modified with Nsuccinimidyl propionate (NSP) or glycine methyl ester (GME) in the presence of a water-soluble carbodiimide, respectively. Based on isoelectric point shift, 4–10 and 10–14 amino groups were modified in the presence of 2 and 4 mM NSP, respectively. Similarly, 3–4 carboxyl groups were modified by reaction with 100 mM GME. Neutralization of negatively charged carboxyl groups with GME did not alter the binding activity of the extrinsic 18 kDa protein. However, the NSP-modified 18 kDa protein, in which the positively charged amino groups had been modified to uncharged methyl esters, failed to bind with the PSII membrane in the presence of the extrinsic 23 kDa protein. This defect can not be attributed to structural or conformational alterations imposed by chemical modification, as the fluorescence and circular dichroism spectra among native, GME and NSP-modified extrinsic 18 kDa proteins were similar. Thus, we have concluded that the positive charges of lysyl residues in the extrinsic 18 kDa protein are important for its interaction with PSII membranes in the presence of the extrinsic 23 kDa protein. Furthermore, it was found that the negative charges of carboxyl groups of this protein did not participate in binding with the extrinsic 23 kDa protein associated with PSII membranes.

Keywords: extrinsic 18 kDa protein; circular dichroism; electrostatic interaction; chemical modification

Journal Article.  0 words. 

Subjects: Biochemistry

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