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Characterization of mouse angiogenin-related protein: implications for functional studies on angiogenin
V Nobile1, B L Vallee, R Shapiro
1Center for Biochemical and Biophysical Sciences and Medicine, Harvard Medical School, Boston, MA 02115, USA.
Abstract:
Angiogenin-related protein (Angrp), the putative product of a recently discovered mouse gene, shares 78% sequence identity with mouse angiogenin (Ang). In the present study, the relationship of Angrp to Ang has been investigated by producing both proteins in bacteria and comparing their functional properties. We find that mouse Ang is potently angiogenic, but Angrp is not, even when assayed at relatively high doses. A deficiency in catalytic capacity, which is essential for the biological activity of Ang, does not appear to underlie Angrp's lack of angiogenicity. In fact, Angrp has somewhat greater ribonucleolytic activity toward tRNA and dinucleotide substrates than does Ang. Instead, an inability to bind cellular receptors is implicated since Angrp does not inhibit Ang-induced angiogenesis. Poor conservation of the Ang receptor recognition sequence 58-69 in Angrp most likely contributes to this defect. However, other substitutions must also influence receptor binding since an Angrp quadruple mutant that is identical to Ang in this segment still lacks both angiogenic activity and the capacity to inhibit Ang. The functional differences between Ang and Angrp, together with evidence presented herein that Angrp is regulated differently than Ang, suggest that the roles of the two proteins in vivo may be quite distinct.
Insights
Angiogenin-related protein (Angrp) is not angiogenic, unlike angiogenin (Ang). Angrp lacks receptor binding but retains ribonucleolytic activity, suggesting distinct biological roles.
Area of Science:
- Molecular Biology
- Biochemistry
- Protein Function
Background:
- Angiogenin-related protein (Angrp) is a newly discovered mouse protein with high sequence identity to angiogenin (Ang).
- Understanding the functional relationship between Angrp and Ang is crucial for elucidating their distinct biological roles.
Purpose of the Study:
- To investigate the functional properties of Angrp compared to Ang.
- To determine the molecular basis for differences in angiogenic activity and receptor binding.
Main Methods:
- Bacterial production of recombinant mouse Ang and Angrp.
- Comparative analysis of angiogenic potential and ribonucleolytic activity.
- Assessment of receptor binding and inhibition of Ang-induced angiogenesis.
Main Results:
- Mouse Ang demonstrated potent angiogenic activity, while Angrp showed no significant angiogenic effect.
- Angrp exhibited comparable or greater ribonucleolytic activity than Ang, indicating catalytic capacity is not the limiting factor.
- Angrp failed to inhibit Ang-induced angiogenesis, suggesting a defect in cellular receptor binding.
- Mutational analysis indicated that while the Ang receptor recognition sequence is poorly conserved in Angrp, other factors also contribute to the lack of receptor interaction.
Conclusions:
- Angrp's lack of angiogenicity is primarily due to impaired cellular receptor binding, not reduced catalytic activity.
- Distinct functional properties and differential regulation suggest Angrp and Ang have separate in vivo functions.