Jack J. Pasternak

Comparison of regulatory and structural regions of the Xenopus laevis small heat-shock protein-encoding gene family

We have isolated several unique Xenopus laevis hsp30 (encoding heat-shock protein 30) genomic clones, one of which contains two complete hsp30 genes (hsp30C and hsp30D), as well as the promoter and N-terminal coding region of a third gene (hsp30E). Nucleotide sequence and restriction enzyme analysis revealed that this gene cluster is different from a cluster isolated previously. The hsp30C and hsp30D genes encode proteins of approx. 24 kDa. In all, the hsp30 gene family contains a minimum of seven genes. The strand exchange and breakage of the duplication events which generated this gene family appear to have occurred within tracts of DNA which potentially can assume a Z-DNA conformation. Comparing the amino acid (aa) sequences of each known Hsp30 protein with bovine alpha-crystallin revealed a high degree of shared conservation of aa that constitute the major structural feature(s) of alpha-crystallin.

The presence of two major protein components in the bovine photoreceptor disc membrane.

Abstract Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of thoroughly washed rod outer segment membrane preparations from bovine retinae revealed two major membrane-bound components and not one as has been generally thought. The higher molecular weight peak (⋍38500 molecular weight) contains a carbohydrate component and is covalently bound to the retinylidene chromophore. Moreover, this material is extensively phosphorylated in vitro upon illumination. Therefore, this component (peak H) is rhodopsin. The nature and function of the other photoreceptor disc membrane component (peak L, ⋍34500 molecular weight) remains to be determined.

Ribosomal and translatable messenger RNA of Eimeria tenella

RNA from oocysts of Eimeria tenella was purified into poly(A)--RNA and poly(A)+-RNA fractions with affinity chromatography on oligo(dT)-cellulose. Gel electrophoresis, under denaturing conditions of the poly(A)--RNA fraction revealed two major RNAs with molecular weights of 1.27 and 0.65 X 10(6). The values for these components not only represent the ribosomal RNAs of this species; but they also resemble the molecular sizes of the non-mRNAs of many other lower eukaryotes. In vitro translation assays with a cell-free wheat germ system showed that the level of translatable mRNA in the poly(A)--RNA fraction was negligible. Virtually all the translatable mRNA in E. tenella was polyadenylated, that is, it contained poly(A)-tracts with more than 15 adenylate residues. Consequently some of the key components of the protein translational machinery of this organism are eukaryotic in nature.

On the Protein Composition of Bovine Rod Outer Segment Disk Membranes

The pigment molecule rhodopsin is generally believed to account for 90% of the total disk membrane protein1. This figure has recently been questioned by Siebert et al.2, who report the existence of three major protein peaks on SDS-PAGE scans, all in the molecular weight region of 30 000 to 42 000. One of the proteins can be washed out, the remaining two, however, are intrinsic. If this peak separation were not artefactual and if only one of the peaks were rhodopsin, it certainly could not constitute 90% of the total disk membrane protein. We have therefore attempted to confirm Siebert’s data and to unequivocally identify rhodopsin among the disk protein components.