Isoforms of gelsolin from lobster striated muscles differ in calcium-dependence

TY - JOUR

T1 - Isoforms of gelsolin from lobster striated muscles differ in calcium-dependence

AU - Unger, Andreas

AU - Brunne, Bianka

AU - Hinssen, Horst

N1 - Copyright © 2013 Elsevier Inc. All rights reserved.

PY - 2013/8/1

Y1 - 2013/8/1

N2 - Two distinct isoforms of the Ca-dependent actin filament severing protein gelsolin were identified in cross-striated muscles of the American lobster. The variants (termed LG1 and LG2) differ by an extension of 18 AA at the C-terminus of LG1, and by two substitutions at AA735 and AA736, the two C-terminal amino acids of LG2. Functional comparison of the isolated and purified proteins revealed gelsolin-typical properties for both with differences in Ca(2+)-sensitivity, LG2 being activated at significant lower Ca-concentration than LG1: Half maximal activation for both filament severing and G-actin binding was ∼4×10(-7)M Ca(2+) for LG2 vs. ∼2×10(-6)M Ca(2+) for LG1. This indicates a differential activation for the two isoproteins in vivo where they are present in almost equal amounts in the muscle cell. Structure prediction modeling on the basis of the known structure of mammalian gelsolin shows that LG2 lacks the C-terminal alpha-helix which is involved in contact formation between domains G6 and G2. In both mammalian gelsolin and LG1, this "latch bridge" is assumed to play a critical role in Ca(2+)-activation by keeping gelsolin in a closed, inactive conformation at low [Ca(2+)]. In LG2, the reduced contact between G6 and G2 may be responsible for its activation at low Ca(2+)-concentration.

AB - Two distinct isoforms of the Ca-dependent actin filament severing protein gelsolin were identified in cross-striated muscles of the American lobster. The variants (termed LG1 and LG2) differ by an extension of 18 AA at the C-terminus of LG1, and by two substitutions at AA735 and AA736, the two C-terminal amino acids of LG2. Functional comparison of the isolated and purified proteins revealed gelsolin-typical properties for both with differences in Ca(2+)-sensitivity, LG2 being activated at significant lower Ca-concentration than LG1: Half maximal activation for both filament severing and G-actin binding was ∼4×10(-7)M Ca(2+) for LG2 vs. ∼2×10(-6)M Ca(2+) for LG1. This indicates a differential activation for the two isoproteins in vivo where they are present in almost equal amounts in the muscle cell. Structure prediction modeling on the basis of the known structure of mammalian gelsolin shows that LG2 lacks the C-terminal alpha-helix which is involved in contact formation between domains G6 and G2. In both mammalian gelsolin and LG1, this "latch bridge" is assumed to play a critical role in Ca(2+)-activation by keeping gelsolin in a closed, inactive conformation at low [Ca(2+)]. In LG2, the reduced contact between G6 and G2 may be responsible for its activation at low Ca(2+)-concentration.

KW - Actins

KW - Amino Acid Sequence

KW - Animals

KW - Arthropod Proteins

KW - Calcium

KW - Gelsolin

KW - Models, Molecular

KW - Molecular Sequence Data

KW - Muscle, Striated

KW - Nephropidae

KW - Protein Conformation

KW - Protein Isoforms

KW - Protein Structure, Secondary

KW - RNA, Messenger

U2 - 10.1016/j.abb.2013.05.005

DO - 10.1016/j.abb.2013.05.005

M3 - SCORING: Journal article

C2 - 23707758

VL - 536

SP - 38

EP - 45

JO - ARCH BIOCHEM BIOPHYS

JF - ARCH BIOCHEM BIOPHYS

SN - 0003-9861

IS - 1

ER -