# SMCT1 has a low affinity to PDZ domain containing 1 protein

## TL;DR

This study shows that SMCT1 binds to PDZ domains in PDZK1, but the interaction is weak and likely not important in the body.

## Contribution

The study experimentally confirms SMCT1-PDZ domain interaction but challenges its physiological relevance.

## Key findings

- SMCT1 binds to two PDZ domains in PDZK1.
- The binding affinity is low, with dissociation constants higher than typical PDZ interactions.

## Abstract

Sodium-coupled monocarboxylate transporter 1 (SMCT1) is a membrane transporter abundantly expressed in colon, kidney, thyroid, brain; and silenced in cancer cells. It transports monocarboxylic acids with little specificity into cells. Based on pulldown experiments, it was proposed that the scaffolding protein PDZ Domain Containing 1 (PDZK1) regulates its surface expression and increases SMCT1’s transportation efficiency. Here, we performed pull-down assays, Surface Plasmon Resonance (SPR), and Micro Scale Thermophoresis (MST) to evaluate the affinity between SMCT1 and two PDZ domains in PDZK1. Our results show that SMCT1 binds to these PDZ domains. However, the estimated equilibrium dissociation constants are higher than in canonical PDZ domains and likely physiological not relevant.