A protein involved in the assembly of an extracellular calcium storage matrix.
Gastroliths, the calcium storage organs of crustaceans, consist of chitin-protein-mineral complexes in which the mineral component is stabilized amorphous calcium carbonate. To date, only three proteins, GAP 65, gastrolith matrix protein (GAMP), and orchestin, have been identified in gastroliths. Here, we report a novel protein, GAP 10, isolated from the gastrolith of the crayfish Cherax quadricarinatus and specifically expressed in its gastrolith disc. The encoding gene was cloned by partial sequencing of the protein extracted from the gastrolith matrix. Based on an assembled microarray cDNA chip, GAP 10 transcripts were found to be highly (12-fold) up-regulated in premolt gastrolith disc and significantly down-regulated in the hypodermis at the same molt stage. The deduced protein sequence of GAP 10 lacks chitin-binding domains and does not show homology to known proteins in the GenBank data base. It does, however, have an amino acid composition that has similarity to proteins extracted from invertebrate and ascidian-calcified extracellular matrices. The GAP 10 sequence contains a predicted signal peptide and predicted phosphorylation sites. In addition, the protein is phosphorylated and exhibits calcium-binding ability. Repeated daily injections of GAP 10 double strand RNA to premolt C. quadricarinatus resulted in a prolonged premolt stage and in the development of gastroliths with irregularly rough surfaces. These findings suggest that GAP 10 may be involved in the assembly of the gastrolith chitin-protein-mineral complex, particularly in the deposition of amorphous calcium carbonate.
Department of Life Sciences, Ben-Gurion University, P. O. Box 653, Beer-Sheva 84105, Israel.
Lilah
L
Glazer
Assaf
A
Shechter
Moshe
M
Tom
Yana
Y
Yudkovski
Simy
S
Weil
Eliahu David
ED
Aflalo
Ramachandra Reddy
RR
Pamuru
Isam
I
Khalaila
Shmuel
S
Bentov
Amir
A
Berman
Amir
A
Sagi
D000825:Animal Structures / Q000378:metabolism; D000818:Animals; D003400:Astacoidea / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D003001:Cloning, Molecular; D005109:Extracellular Matrix / Q000235:genetics / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis* / Q000235:genetics; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000502:physiology*; D008297:Male; D008969:Molecular Sequence Data; D018978:Molting / Q000502:physiology; D020411:Oligonucleotide Array Sequence Analysis
D002135:Calcium-Binding Proteins; D016326:Extracellular Matrix Proteins; D002118:Calcium