fosfattransport

Fosfattransport, or phosphate transport, refers to the movement of inorganic phosphate (Pi) across biological membranes. Phosphate is essential for energy metabolism, nucleic acids, and many biosynthetic processes, making its acquisition, distribution, and regulation a fundamental aspect of cellular physiology. Transport systems vary by organism and tissue and can be regulated by phosphate availability.

Bacteria and fungi use multiple uptake systems. In bacteria, two major pathways operate: the Pit (low-affinity inorganic phosphate transporter) and the high-affinity PstSCAB ABC transporter. PstSCAB consists of a periplasmic phosphate-binding protein (PstS) and membrane components (PstC, PstA) with an ATPase (PstB) that powers transport. Expression of these systems is coordinated by the Pho regulon through the PhoR-PhoB two-component system, which activates genes under phosphate starvation. Similar high- and low-affinity strategies occur in other microbes, enabling uptake across a range of environmental Pi concentrations.

In plants, phosphate uptake from soil is mainly mediated by the PHT1 family of plasma membrane transporters, which are largely proton-coupled. Plant Pi uptake is tightly regulated by Pi status, transcription factors such as PHR1, SPX domain proteins, and microRNAs (e.g., miR399). Under Pi limitation, plants also engage with arbuscular mycorrhizal fungi to access soil Pi via a symbiotic pathway.

In animals, phosphate transport is mediated by two major families: the SLC34 and SLC20 families. SLC34 transporters (NaPi-IIa, IIb, IIc) are sodium-dependent cotransporters involved in intestinal absorption and renal reabsorption. SLC20 transporters (PiT-1, PiT-2) also participate in phosphate uptake in various tissues. Regulation involves hormonal signals (e.g., vitamin D, parathyroid hormone) and systemic Pi balance.

Overall, phosphates are moved by specialized transporters that couple Pi movement to electrochemical gradients or ATP hydrolysis, reflecting the diverse physiological roles of phosphate in biology.