Isoenzyme-specific interaction of muscle-type creatine kinase with the sarcomeric M-line is mediated by NH(2)-terminal lysine charge-clamps.
Creatine kinase (CK) is located in an isoenzyme-specific manner at subcellular sites of energy production and consumption. In muscle cells, the muscle-type CK isoform (MM-CK) specifically interacts with the sarcomeric M-line, while the highly homologous brain-type CK isoform (BB-CK) does not share this property. Sequence comparison revealed two pairs of lysine residues that are highly conserved in M-CK but are not present in B-CK. The role of these lysines in mediating M-line interaction was tested with a set of M-CK and B-CK point mutants and chimeras. We found that all four lysine residues are involved in the isoenzyme-specific M-line interaction, acting pair-wise as strong (K104/K115) and weak interaction sites (K8/K24). An exchange of these lysines in MM-CK led to a loss of M-line binding, whereas the introduction of the very same lysines into BB-CK led to a gain of function by transforming BB-CK into a fully competent M-line-binding protein. The role of the four lysines in MM-CK is discussed within the context of the recently solved x-ray structures of MM-CK and BB-CK.
Hornemann
T
T
Swiss Federal Institute of Technology, Institute of Cell Biology, Eidenössisch Technische Hochschule Zürich Hönggerberg, 8093 Zürich, Switzerland. horneman@cell.biol.ethz.ch
Stolz
M
M
Wallimann
T
T
D000595:Amino Acid Sequence; D000818:Animals; D003402:Creatine Kinase / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D007527:Isoenzymes; D008239:Lysine / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D016658:Psoas Muscles / Q000201:enzymology*; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012518:Sarcomeres / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D003402:Creatine Kinase; D008239:Lysine