Solution X-ray scattering data show structural differences among chimeras of yeast and chicken calmodulin: implications for structure and function.
We present here the first evidence, obtained by the use of small-angle X-ray scattering, of the solution structures of chimeras constructed from yeast (Saccharomyces cerevisiae, Sc) and chicken (Gallus gallus, Gg) calmodulin (CaM). The chimeric proteins used in this study are Sc(1-129)/Gg(130-148), Sc(1-128)/Gg(129-148), Sc(1-87)/Gg(88-148), and Sc(1-72)/Gg(73-148) CaMs, in which Sc(1-)(n)() and Gg(()(n)(+1)-148) descend from yeast and chicken CaM in the chimeric proteins, respectively. Under the Ca(2+)-saturated condition, the solution structure of Sc(1-128)/Gg(129-148) CaM has a dumbbell-like shape which is characteristic of vertebrate-type CaM, while that of Sc(1-129)/Gg(130-148) CaM takes an intermediate structure between the dumbbell-like shape and a compact globular shape. The results provide the direct evidence that the replacement of Asp(129) with Ser(129) induces an interaction between two lobes of Sc(1-129)/Gg(130-148) CaM and brings them close together. It implies that a site interacting with the N-lobe is induced in the C-lobe, although site IV that is unable to bind Ca(2+) hinders the ability of the C-lobe to undergo the conformational change to the full open state. In the presence of both Ca(2+) and a peptide synthesized to mimic the CaM binding domain on myosin light chain kinase, MLCK-22p, the solution structures of these chimeric CaMs take a similar compact globular shape but their interactions are quite different. The solution structure and interactions of Sc(1-72)/Gg(73-148) CaM are similar to those of Sc(1-87)/Gg(88-148) CaM. The structure of Sc(1-87)/Gg(88-148) CaM is similar to that of Sc(1-128)/Gg(129-148) CaM, but their interactions are different. The result indicates that the replacement of Glu(119) with Ala(119) has a critical effect on their interactions. Thus, the functional differences among these chimeric CaMs, which have been reported previously [Nakashima, K., et al. (1996) Biochemistry 35, 5602-5610], have been interpreted on the basis of the structures and interactions.
Yokouchi
Tsuyoshi
T
Graduate Program of Human Sensing and Functional Sensor Engineering, Graduate School of Science and Engineering, Yamagata University, Yonezawa 992-8510, Japan.
Nogami
Hideki
H
Izumi
Yoshinobu
Y
Yoshino
Hidenori
H
Nakashima
Ken-ichi
K
Yazawa
Michio
M
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000737:chemistry; D002147:Calmodulin / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D002417:Cattle; D002645:Chickens; D008956:Models, Chemical; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000201:enzymology; D009219:Myosin-Light-Chain Kinase / Q000737:chemistry / Q000235:genetics; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D012542:Scattering, Radiation; D012996:Solutions; D013329:Structure-Activity Relationship; D014965:X-Rays
D002147:Calmodulin; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D012996:Solutions; D009219:Myosin-Light-Chain Kinase; D002118:Calcium