A cryptobiosis-specific 19S protein complex of Artemia salina gastrulae

Abstract

The postribosomal supernatant of Artemia salina cryptobiotic embryos contains a large quantity of a 19S protein complex. An amount of 3.6 mg/g of cysts is measured by immunoprecipitation with anti-(19S protein complex) antibody. The quantity of this complex decreases during further development to nauplius larvae to only 15% of the quantity present in cryptobiotic embryos. The complex was no longer detectable after 7 days of growth. The 27000-Mr protein subunit of the 19S complex is not synthesized by mRNA isolated from cryptobiotic embryos. The cryptobiosis-specific complex has Mr 573000 and 610000 as calculated from light-scattering and sedimentation-diffusion measurements respectively. The 19S homocomplex contains 20-23 27000-Mr proteins and has no function in the translation of homologous mRNA. From hydrodynamic data a hydration of 1.25 g of water/g of protein is calculated. The abundant presence of the 19S protein complex in cryptobiotic embryos and the absence of synthesis during development to nauplius larvae indicate a functional role during the cryptobiotic process in early embryogenesis. A role in maintaining the water content of the cytoplasm above a critical threshold during desiccation is suggested.

Identification and properties of the 38000‐M, poly(A)‐binding protein of non‐polysomal messenger ribonucleoproteins of cryptobiotic gastrulae of Artemia salina

“…The amount of poly(A) and P38 was calculated from the specific activity of the polynucleotide and with anti-P38 antiserum respectively. A stoichiometry of one protein per 9 2 nucleotides was obtained in agreement with the results of filter binding [26] (Table 1). Although P38 is located on the poly(A) sequence of non-polysomal mRNP of Artemia salina [26] it is able to interact with other RNA sequences.…”

“…The absorption coefficient of P38 is = 9.0cm- [26]. Small concentrations of P38 were measured by immunoprecipitation.…”

“…Proteins eluted with 1 M KC1 rrom oligo(dT)-cellulose-bound RNP were dialyzed against buffer S and fractionated by ion-exchange chromatography on phosphoccllulose PI 1. Bound proteins were eluted with a salt gradient from S0mM KCI to 400mM KCI in buffer S. P38 eluted at 200mM KCI and was further purified by affinity chromatography on poly(h)-Sepharose 4B as described [26]. The helix-destabilizing protein HD40 was prepared according to Marvil et al [30].…”

“…Analysis of proteins by electrophoresis on 10% (w/v) polyacrylamide/dodecyl sulphate gels was as described [26]. Two-dimensional gel electrophoresis was performed according to the procedure of O'Farrell [37].…”

Purification of a RNA-binding Protein from Rat Liver

“…From Artemia cysts the protein artemin was purified, which shared homology with vertebrate ferritins and probably functions as iron storage protein (30). In addition, artemin belongs to a class of RNAbinding proteins and was proposed to maintain the integrity of the dehydrated cyst (31,32).…”