Trying to rotate a 2D sprite

I've got this code attached to a 2D sprite that I want to rotate. So far I'm working on making it rotate left when the left arrow key is pressed. I get no parsing errors, but when I run the game, the code doesn't work. Any idea what I'm doing wrong?

 using UnityEngine;
 using System.Collections;
 
 public class Rotate : MonoBehaviour {
 
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
 
         if (Input.GetButtonDown ("left"))
             RotateLeft();
     }
 
     void RotateLeft () {
         Quaternion theRotation = transform.localRotation;
         theRotation.z *= 270;
         transform.localRotation = theRotation;
     }
 }