BIOINORGANIC CHEMISTRY A Short Course Second Edition

CALCIUM-DEPENDENT MOLECULES 315

Clore, Gronenborn, Bax, and co - workers published the three - dimensional
solution structure of the complex between Ca 2+ - saturated calmodulin and a
26 - residue synthetic peptide comprised of the calmodulin - binding domain of
rabbit skeletal muscle myosin light chain kinase (skMLCK, also referred to as
M13) in 1992 (PDB: 2BBM).^85 They noted that the N - terminal (residues 6 – 73)
and C - terminal (residues 83 – 146) calmodulin domains remained essentially
unchanged upon complexation with the peptide. However, the central linker
region (residues 65 – 93), helical in Ca 2+ - saturated calmodulin as determined by
published X - ray crystallographic structures (PDB: 3CLN, reference 71 ) but
disrupted near its midpoint in solution structures, also appears disrupted into
a long fl exible loop in the PDB: 2BBM structure. In fact, the central region
(residues 74 – 82) appears to be a fl exible linker between the N - and C - terminal
domains changing Ca 2+ - saturated calmodulin from an “ extended ” dumbbell
shape with dimensions of approximately 65 × 30 × 30 Å into a “ collapsed ”
globular complex of ellipsoidal shape measuring 47 × 32 × 30 Å. The 26 - residue

9

(6)

10

(7)

11

(8)

12

(9)

13

(10)

14

(11)

15

(12)

16

(13)

17

(14)

18

(15)

19

(16) 20 21 22 23 24

I A V S A A N R F K K I S S S G

H A V R A I G R L S S

L T T M L A T R N F S

N A T A V V R H M

N R I Q T Q I K

N R I Q T Q I K V V N A F S S S

N R I Q T Q I K V V N A F S S S

L V K S M L R K R S F G N P F

L V K A M G H R K R F G N P F R

F S F K K