ISSN:
1573-4919
Keywords:
Protochordate muscle
;
Cyclostome muscle
;
Ca2+-binding proteins
;
Amphioxus
;
Lamprey
;
Vertebrate-invertebrate junction
;
Mg2+-binding
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Summary A sarcoplasmic calcium-binding protein (SCP) has been purified from the muscle of the protochordate Amphioxus and shown to be more similar to invertebrate SCP's than to their counterpart found in vertebrates, i.e. parvalbumins. The Amphioxus protein has a pI of 4.9, is rich in tyrosine and tryptophan, has a molecular weight of 22,000 and binds strongly 2Ca2+ with a pK of 7.88. Magnesium competes with calcium for only one of the two metal-binding sites and induces positive cooperativity in Ca2+ binding. In cyclostome muscle (lamprey and hagfish), no protein with high affinity for Ca2+ or Mg2+ could be found, irrespective of molecular weight. Instead, a protein with moderate affinity for Ca2+ (⩽105 m −1) was detected: it has a molecular weight of 60,000 and might be quite ubiquitous, as the presence of a similar protein has been reported both in red and white muscle of vertebrates such as chicken and rabbit.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00241386
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