Hemoglobin as an proto-photoreceptor

Preprint draft Receptors can exhibit duality and multimodality in sensing.1 I proposed hemoglobin as an gasoreceptor and aquareceptor in proto- or split-component signaling transduction systems due to its catalytic activity- or its (“partner”) signal transducer-dependent signaling, respectively.2,3 But if hemoglobin can be considered as an gasoreceptor or aquareceptor, it raises a question on its well-established photodissociation property-induced gasocrine process that can occur at femtosecond timescales.4,5 However, unlike oxygen or carbon monoxide or nitric oxide or other gaseous molecules that can considered as a competitive inhibitor of hemoglobin’s catalytic activity, photon cannot be considered a competitive inhibitor of hemoglobin. Nevertheless, the photon-dependent photodissociation either in hemoglobin or in other globins depending on the quantum yield, rebinding/geminate recombination rates can trigger either gasocrine or thermocrine or reactive species-dependent signaling.4,5 Based on these facts, and building upon others proposal as hemoglobin as an photoreceptor,6 I propose hemoglobin (and other hemoproteins) as a proto-photoreceptor that can signal via thermocrine signaling or gasocrine signaling or other reactive species-dependent signaling. But that does not exclude the possibility of such proteins to act as a photoreceptor in split-component signal transduction system. It is also worth debating on the evolutionary role of globins.7 As some globins can phase separate, be secreted, and even crystallize in vivo, was the evolutionary role was in gas transport or detoxification or was it photon sink or a light-dependent defense response?8–10 Or all of them depending on the environment? Extending upon the role of heme in hemoglobin in photoreception, the role of free heme and nucleic acid-bound heme needs to be also considered as a non-protein-based proto-photoreceptor and proto-photoriboceptor, respectively.11 Finally, another question arises on the role of photosynthesis-capable microorganism-dependent atmospheric gases vs non-biotic origin of atmospheric gases.12,13 If photodissociation is a general phenomenon, then the precise contributions of it in the origin and concentration of atmospheric gases needs to be precisely evaluated. This will help understand the role of abiotic factors in planetary gasocrinology.14 REFERENCE 1. Anbalagan S. Sugar-sensing swodkoreceptors and swodkocrine signaling. Animal Model Exp Med 2025; 8:944–61. 2. Anbalagan S. Hemoglobin as an oxygen gasoreceptor. Acta Biochim Pol 2025; 72:15546. 3. Anbalagan S. [Heme-based aquareceptors]. Postepy Biochem 2024; 70:420–3. 4. Noble RW, Brunori M, Wyman J, Antonini E. Studies on the quantum yields of the photodissociation of carbon monoxide from hemoglobin and myoglobin. Biochemistry 1967; 6:1216–22. 5. Eaton WA, Henry ER, Hofrichter J, Bettati S, Viappiani C, Mozzarelli A. Evolution of allosteric models for hemoglobin. IUBMB Life 2007; 59:586–99. 6. Oren DA, Koziorowski M, Desan PH. SAD and the not-so-single photoreceptors. Am J Psychiatry 2013; 170:1403–12. 7. Vinogradov SN, Hoogewijs D, Bailly X, Arredondo-Peter R, Gough J, Dewilde S, Moens L, Vanfleteren JR. A phylogenomic profile of globins. BMC Evolutionary Biology 2006; 6:31. 8. Burr AH, Harosi FI. Naturally crystalline hemoglobin of the nematode Mermis nigrescens. An in situ microspectrophotometric study of chemical properties and dichroism. Biophys J 1985; 47:527–36. 9. Roy U, Kornitzer D. Heme-iron acquisition in fungi. Curr Opin Microbiol 2019; 52:77–83. 10. Zhang F, Zhang B, Wang Y, Jiang R, Liu J, Wei Y, Gao X, Zhu Y, Wang X, Sun M, et al. An extra-erythrocyte role of haemoglobin body in chondrocyte hypoxia adaption. Nature 2023; 622:834–41. 11. Anbalagan S. Gas-sensing riboceptors. RNA Biol 2024; 21:1–6. 12. Thannickal VJ. Oxygen in the Evolution of Complex Life and the Price We Pay. Am J Respir Cell Mol Biol 2009; 40:507–10. 13. Canfield DE. Oxygen: A Four Billion Year History. Princeton, New Jersey, USA: Princeton University Press; 2014. 14. Anbalagan S. Planetary Gasocrinology [Internet]. 2025 [cited 2025 Sept 9]; Available from: https://zenodo.org/records/17052709