Small-angle scattering studies show distinct conformations of calmodulin in its complexes with two peptides based on the regulatory domain of the catalytic subunit of phosphorylase kinase.
Small-angle X-ray and neutron scattering have been used to study the solution structures of calmodulin complexed with synthetic peptides corresponding to residues 342-366 and 301-326, designated PhK5 and PhK13, respectively, in the regulatory domain of the catalytic subunit of skeletal muscle phosphorylase kinase. The scattering data show that binding of PhK5 to calmodulin induces a dramatic contraction of calmodulin, similar to that previously observed when calmodulin is complexed with the calmodulin-binding domain peptide from rabbit skeletal muscle myosin light chain kinase. In contrast, calmodulin remains extended upon binding PhK13. In the presence of both peptides, calmodulin also remains extended. Apparently, the presence of PhK13 inhibits calmodulin from undergoing the PhK5-induced contraction. These data indicate that there is a fundamentally different type of calmodulin-target enzyme interaction in the case of the catalytic subunit of phosphorylase kinase compared with that for myosin light chain kinase.
Trewhella
J
J
Life Sciences Division, Los Alamos National Laboratory, New Mexico 87545.
Blumenthal
D K
DK
Rokop
S E
SE
Seeger
P A
PA
D000595:Amino Acid Sequence; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D009219:Myosin-Light-Chain Kinase / Q000737:chemistry / Q000378:metabolism; D009502:Neutrons; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D010764:Phosphorylase Kinase / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D012542:Scattering, Radiation; D014965:X-Rays
D002147:Calmodulin; D010455:Peptides; D010764:Phosphorylase Kinase; D009219:Myosin-Light-Chain Kinase