Structure and function of the human sperm-specific isoform of protein kinase A (PKA) catalytic subunit C伪2

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• 作者：Tuva H. Hereng^a ; Paul H. Backe^b ; ^c ; ^d ; Jan Kahmann^e ; Christoph Scheich^e ; Magnar Bj&oslash ; rå ; s^b ; ^c ; ^d ; Bj&oslash ; rn S. Skå ; lhegg^a ; ^f ; Ken R. Rosendal^a ; ^{ken.rosendal@gmail.com} ; ^{ken@spermatech.com}
• 关键词：AKAP ; A-kinase anchoring proteins ; C ; catalytic subunit ; CSP ; chemical shift perturbations ; FS ; fibrous sheath ; MEGA8 ; octanoyl-N-methylglucamide ; MEGA10 ; decanoyl-N-methylglucamide ; MTAB ; myristoyltrimethylammonium bromide ; NaCN ; sodium cyanide ; PKI ; pro
• 刊名：Journal of Structural Biology
• 出版年：2012
• 期刊代码：92_10478477
• 类别：ph
• 出版时间：June, 2012
• 卷：178
• 期：3
• 页码：300-310
• 文件大小：1418 K

摘要

Protein kinase A (PKA) exists as several tissue-specific isoforms that through phosphorylation of serine and threonine residues of substrate proteins act as key regulators of a number of cellular processes. We here demonstrate that the human sperm-specific isoform of PKA named C伪2 is important for sperm motility and thus male fertility. Furthermore, we report on the first three-dimensional crystal structure of human apo C伪2 to 2.1 脜. Apo C伪2 displays an open conformation similar to the well-characterized apo structure of murine C伪1. The asymmetric unit contains two molecules and the core of the small lobe is rotated by almost 13掳 in the A molecule relative to the B molecule. In addition, a salt bridge between Lys72 and Glu91 was observed for C伪2 in the apo-form, a conformation previously found only in dimeric or ternary complexes of C伪1. Human C伪2 and C伪1 share primary structure with the exception of the amino acids at the N-terminus coded for by an alternative exon 1. The N-terminal glycine of C伪1 is myristoylated and this aliphatic chain anchors the N-terminus to an intramolecular hydrophobic pocket. C伪2 cannot be myristoylated and the crystal structure revealed that the equivalent hydrophobic pocket is unoccupied and exposed. Nuclear magnetic resonance (NMR) spectroscopy further demonstrated that detergents with hydrophobic moieties of different lengths can bind deep into this uncovered pocket. Our findings indicate that C伪2 through the hydrophobic pocket has the ability to bind intracellular targets in the sperm cell, which may modulate protein stability, activity and/or cellular localization.